i
Fed-Std-376B

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Foreword

This standard was developed by the Standards and Metric Practices

Subcommittee of the Metrication Operating Committee, which operates under the

Interagency Council on Metric Policy. It is the basic Federal standard that lists

metric units recommended for use throughout the Federal government, and is

specified in the Federal Standardization Handbook, issued by the General

Services Administration in accordance with 41 CFR 101-29. Before issue, it was

coordinated with the departments and agencies of the Interagency Council on

Metric Policy.

The General Services Administration has authorized the use of this Federal

standard by all Federal agencies.

Civilian Agency Coordinating Activity:

Federal Supply Service, General Services Administration

Military Agency Coordinating Activity:

Standardization Program, Office of the Assistant Secretary

(Production and Logistics), Department of Defense

Preparing Activity:

Metric Program, National Institute of Standards and Technology,

Technology Administration, Department of Commerce

Changes

When a federal agency determines that there is a need for a revision of this

standard, a written request for revision should be submitted to the General

Services Administration, Federal Supply Service, Environmental and Engineering

Policy Division (FCRE), Washington, DC 20406. The request shall include data

that support the proposed change. The Metric Program, National Institute of

Standards and Technology, as custodian of this standard, will coordinate all

proposed changes with the Metrication Operating Committee.
Fed. Std. 376B

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Table of Contents

1. Scope .................................................................. 1

2. Authoritative Document ....................................... 1

3. Definitions............................................................ 1

4. General Requirements ........................................ 1

5. Detailed Requirements ........................................ 8

Bibliography............................................................ 21

Alphabetical Index .................................................. 23
Fed. Std. 376B

1

1. SCOPE

This standard lists preferred metric units (See 4.1) recommended for use

throughout the Federal Government. It gives guidance on the selection of

metric units required to comply with the provisions of the Metric Conversion

Act of 1975 (P.L. 94-168), as amended by the Omnibus Trade and

Competitiveness Act of 1988 (P.L. 100-418), and Executive Order (EO)

12770 of July 25, 1991. The guidance in this standard applies to, but is not

limited to, the drafting of laws, regulations, contracts, and purchase orders;

and the preparation of reports, statistical tables, and databases.

2. AUTHORITATIVE DOCUMENT

The following document forms the authoritative basis of this standard to the

extent specified herein:

American National Standard for Metric Practice, ANSI/IEEE Std 268-1992,

Institute of Electrical and Electronics Engineers, Inc.

3. DEFINITIONS

3.1 SI Units. Units belonging to the International System of Units, which is

abbreviated SI (from the French Le Système International d'Unités), as

interpreted or modified for use in the United States by the Secretary of

Commerce (55 F.R. 52242, Dec. 20, 1990).

3.2 Inch-pound Units. Units based upon the yard and the pound, commonly

used in the United States, and defined by the National Bureau of Standards

(now the National Institute of Standards and Technology). In this standard,

the term inch-pound unit includes other customary units, such as the degree

Fahrenheit, used extensively in the United States at present. Some inchpound units used in the United States, such as the gallon, have the same

name as units previously used in other countries but differ in magnitude.

4. GENERAL REQUIREMENTS

4.1 Preferred Metric Units. Preferred metric units for use throughout the

Federal Government are:

The SI units (together with their multiples and

submultiples);

Three other metric units—the liter, hectare, and

metric ton—that are accepted for use with
Fed. Std. 376B

2

the SI units because of their practical

importance; and

A small number of other metric units, listed in Section

5, that are accepted because of their use in

specialized fields. 

The preferred metric units listed in Section 5 of this standard have been

selected in accordance with the recommendations of ANSI/IEEE Std 268.

4.1.1SI Base Units and Supplementary Units. The SI is constructed from

seven base units for independent quantities1

 plus the two supplementary

units for plane angle and solid angle. 

Quantity Unit Name Unit Symbol

length meter m

mass2 kilogram kg

time second s

electric current ampere A

thermodynamic temperature kelvin K

amount of substance mole mol

luminous intensity candela cd

plane angle radian rad

solid angle steradian sr

4.1.2SI Derived Units. Derived units are formed by combining base units,

supplementary units, and other derived units according to the algebraic

relations linking the corresponding quantities. The symbols for derived units

are obtained by means of the mathematical signs for multiplication, division,

and use of exponents. For example, the SI unit for velocity is the meter per

second (m/s or m⋅ s-1), and that for angular velocity is the radian per second

(rad/s or rad⋅ s-1). Some derived SI units have been given special names and

symbols, as follows:

 

 1 As used in this standard, "quantity" is the technical word for measurable attributes of phenomena or matter.

 2 In commercial and everyday use, and in many technical fields, the term "weight" is usually used as a synonym for mass. 

This is how "weight" is used in most United States laws and regulations. See the note at 5.2.1 for further explanation.
Fed. Std. 376B

3

Quantity Unit Name Unit Symbol Expression in

Terms of Other

SI Units

Absorbed dose, specific,

energy imparted, kerma,

absorbed dose index

gray Gy J/kg

Activity (of a radionuclide) becquerel Bq 1/s

Celsius temperature degree Celsius °C K

Dose equivalent sievert Sv J/kg

Electric capacitance farad F C/V

Electric charge, quantity of

electricity

coulomb C A⋅ s

Electric conductance siemens S A/V

Electric inductance henry H Wb/A

Electric potential, potential

difference, electromotive

force

volt V W/A

Electric resistance ohm Ω V/A

Energy, work, quantity of heat joule J N⋅ m

Force newton N kg⋅ m/s2

Frequency (of a periodic

phenomenon)

hertz Hz 1/s

Illuminance lux lx lm/m2

Luminous flux lumen lm cd⋅ sr

Magnetic flux weber Wb V⋅ s

Magnetic flux density tesla T Wb/m2

Power, radiant flux watt W J/s

Pressure, stress pascal Pa N/m2

4.1.3SI Prefixes. The common metric prefixes are:

Multiplication Factor Prefix Name Prefix Symbol

1 000 000 000 000 = 1012 tera T

1 000 000 000 = 109 giga G

1 000 000 = 106 mega M

1 000 = 103 kilo k

100 = 102 hecto h

10 = 101 deka da

0.1 = 10-1 deci d

0.01 = 10-2 centi c

0.001 = 10-3 milli m

0.000 001 = 10-6 micro μ

0.000 000 001 = 10-9 nano n

0.000 000 000 001 = 10-12 pico p
Fed. Std. 376B

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These prefixes are part of SI. They are attached to an SI unit name or symbol

to form what are properly called "multiples" and "submultiples" of the SI unit. 

Prefixes produce units that are of an appropriate size for the application, e.g.,

millimeter or kilometer. Examples that show reasonable choices of multiples

and submultiples for many practical applications are given in Section 5. While

all combinations are technically correct, many are not used in practice. The

prefixes deci, deka, and hecto are rarely used; prefixes that are multiples or

submultiples of 1000 are generally preferred. When the unit name is written in

full, the prefix is written in full: megahertz, not Mhertz. When the unit symbol

is used, the prefix symbol is used: MHz, not megaHz. Only one prefix should

be used in forming a multiple of an SI unit, e.g., Mg, not kkg; or μV, not mmV. 

Prefix symbols for the values a million or greater are capitalized and those

below a million are written in lower case. 

4.1.4Editorial Style. The names of all SI units begin with a lower case letter

except, of course, at the beginning of a sentence or when other grammar rules

dictate capitalizing nouns. There is one exception: in "degree Celsius" the

term "degree" is lower case but "Celsius" is always capitalized. Unit symbols

are always written in lower case except for the liter and those units derived

from the name of a person (e.g., W for watt, Pa for pascal, etc.). SI symbols

are unique "letter shorthand" for unit names—they are not abbreviations and

should therefore not be followed by a period (except at the end of a sentence).

 Likewise, symbols stand for both the singular and plural of the unit and should

not have an "s" added. SI units are always written in an upright typeface with

a space between the numeric value and the symbol. See ANSI/IEEE Std 268

and other documents listed in the Bibliography for further usage rules.

4.2 Accepted Units. For practical reasons a number of non-metric units are

accepted for use. These include units of time (minute, hour, etc.), units of plane

angle (degree, etc.), and a few units for special applications, such as the

nautical mile, used in navigation. Section 5 includes accepted units and shows

their areas of application. These units may be used in full compliance with the

provisions of the amended Metric Conversion Act, EO 12770, and the Federal

Register Notice, "Metric System of Measurement; Interpretation of the

International System of Units for the United States" (55 F.R. 52242, Dec. 20,

1990).

4.3 Unacceptable Metric Units. Many older metric practices do not comply with

the amended Metric Conversion Act, EO 12770, and 55 F.R. 52242. Particular

care shall be taken to avoid introducing non-SI practices into the United States

in areas where such practices are not now established. The units listed in the

following three subsections shall not be used.

4.3.1 CGS Units. Units with special names peculiar to the various cgs
Fed. Std. 376B

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(centimeter-gram-second) systems shall not be used. Among these units are

the following that have been commonly used:

erg, dyne, gal used in mechanics;

poise, stokes used in fluid dynamics;

stilb, phot, lambert used in photometry;

emu, esu, gauss, oersted,

maxwell, gilbert, biot,

franklin, abampere, abvolt,

statvolt, etc.

used in electricity and magnetism.

4.3.2 Deprecated Names or Symbols. Other units from older versions of the

metric system and metric jargon that shall not be used include:

Incorrect term Correct Unit

kilo kilogram

are square dekameter

candle or

candlepower candela

fermi femtometer

gamma nanotesla

micron micrometer

millimicron nanometer

mho siemens

γ microgram

λ cubic millimeter or microliter

4.3.3 Miscellaneous Non-SI Units Not to be Used. Additional units

that are not accepted for use include the following:

ångström

calorie

g as a unit of acceleration (g = 9.81 m/s2

)

grade or gon [1 grade = (π/200) rad]

kilogram-force

langley (1 langley = 1 cal/cm2

)

metric carat

metric horsepower

millimeter of mercury

millimeter, centimeter, or meter of water

standard atmosphere (101.325 kPa)

technical atmosphere (98.0665 kPa)

torr (133.322 Pa)
Fed. Std. 376B

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4.4 Conversion. Conversion factors in Section 5 are shown from inch-pound

units to metric units, generally to seven significant digits. The first column,

labeled From, lists inch-pound and other units commonly used to express the

quantities; the second column, labeled To, gives SI units or other preferred

units; and the third column, labeled Multiply By, gives the conversion factors by

which the numerical value in From units must be multiplied to obtain the

numerical value in To units. For conversion from inch-pound units to metric

units, multiply by the factor. For example, to convert 10.1 feet to meters

multiple by 0.3048; the answer is 3.078 meters, which can be rounded to 3.08

meters (see Section 4.5 on rounding). For conversion from metric units to inchpound units, divide rather than multiply by the factor. For example, to convert

16.3 meters to yards divide by 0.9144; the answer is 17.826 yards, which can

be rounded to 17.8 yards.

4.5 Rounding. For rounding of metric values obtained by conversion from inchpound values, the following simplified rules are suggested. A more complete

treatment of rounding rules is given in Appendix C of ANSI/IEEE Std 268.

4.5.1 If the inch-pound value is expressed by a combination of units such as

feet and inches, or pounds and ounces, it should first be converted to the

smaller unit.

Examples: 12 ft 5 in = 149 in

1 lb 3-1/2 oz = 19.5 oz

4.5.2 Multiply the inch-pound value by the conversion factor. If the first

significant3 digit of the metric value is equal to or greater than the first

significant digit of the inch-pound value, round the metric value to the same

number of significant digits as there are in the inch-pound value.

Examples: 11 mi x 1.609 = 17.699 km, which rounds to 18 km

61 mi x 1.609 = 98.149 km, which rounds to 98 km

If the first significant digit of the metric value is smaller than the first

significant digit of the inch-pound value, round to one more significant digit.

Examples: 66 mi x 1.609 = 106.194 km, which rounds to 106 km

8 ft x 0.3048 = 2.4384 m, which rounds to 2.4 m

4.5.3 When the digits to be discarded begin with a 5 or more, increase the last

 

 3One or more zeroes at the beginning of a number are not treated as significant.
Fed. Std. 376B

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digit retained by one.

Example: 8.3745, if rounded to three digits, would be 8.37; if rounded to

four digits, would be 8.375.

4.5.4 It is essential to use good judgment in estimating the precision required in

conversions.

Example: A length given as 8 ft would ordinarily convert to 2.4 m. If, however,

the measurement given as 8 ft is believed to be valid to the nearest 1/10

inch, it should be treated as 8.00 feet and considered as having three

significant digits. The rounded dimension would then be 2.438 m instead of

2.4 m.

Do not retain more digits than is appropriate for the situation.

Example: A nautical chart shows a landmark to be 75 ft in height; from

subsection 4.5.2 this rounds to 22.8 m, but a value of 23 m would be more

reasonable for the application.

4.5.5 Where an inch-pound value represents a maximum or minimum limit that

must be respected, the rounding must be in the direction that does not violate

the original limit.

Example: For most applications 10 ft rounds to 3 m, but if a safety code

requires 10 feet of clearance from a high voltage line, a conversion to 3.05

meters must be used until new studies show 3 meters of clearance to be

sufficient.

4.5.6 Normally, temperatures expressed in a whole number of degrees

Fahrenheit should be converted to the nearest 0.5 K (or degree Celsius). As

with other quantities, the number of significant digits to retain will depend upon

the implied accuracy of the original temperature.
Fed. Std. 376B

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5. DETAILED REQUIREMENTS

This section gives detailed requirements for the selection of units, consistent with

ANSI/IEEE Std 268. The subsections list conversion factors to the appropriately

sized metric unit, either an SI unit with appropriate prefix or a non-SI unit that is

accepted for use with SI. ANSI/IEEE Std 268, which has been recommended by

the Metrication Operating Committee of the Interagency Council on Metric Policy

for use by all agencies and departments of the Federal Government, lists

conversion factors to SI units only. The SI units are the coherent set of base,

supplementary, and derived units without prefixes, except for the base unit

kilogram.

Government agencies may develop supplemental lists of accepted units applicable

to their special fields. Such supplemental lists shall be consistent with this Federal

Standard and with ANSI/IEEE Std 268.

Other Derived Quantities. It is not practical to list all quantities, but others not

listed can be readily derived using the conversion factors given. For example,

to convert from inches per second to centimeters per second, multiply by 2.54;

to convert from Btu per pound to joules per kilogram, multiply by

(1055.056)/(0.453 592 37) or 2326.

Note on Mixed Units and Fractions. Mixed units, which are commonly used

with inch-pound units, are not used in metric practice. Thus, while a distance

may be given in inch-pound units as 27 ft, 5 in, metric practice shows a length

as 3.45 m rather than 3 m, 45 cm. Binary fractions (such as 1/2 or 3/8) are not

used with metric units. For example, a person's weight is given as 70.5 kg, not

70-1/2 kg.

Preferred units for various quantities are grouped in the following subsections by: 

Space and Time, Mechanics, Heat, Electricity and Magnetism, Light, and

Radiology. (These groupings are consistent with the groupings in ANSI/IEEE Std

268.) The quantities under each group are listed in italic type. The first column,

labeled From, lists inch-pound and other units commonly used to express the

quantities; the second column, labeled To, gives SI units or other preferred units;

and the third column, labeled Multiply By, gives the conversion factors (generally

to seven significant digits) by which the numerical value in From units must be

multiplied to obtain the numerical value in To units. SI units and their submultiples

or multiples, in the To column, are in bold type. The liter, hectare, and metric ton

and other accepted units (see 4.2), in the To column, are in normal type. 

Conversion factors, in the Multiply By column, that are exact are in bold type.
Fed-Std-376B

From To Multiply By

9

5.1 Quantities of Space and Time

5.1.1 Plane angle

NOTE: No change in U.S. customary usage is required for plane angle units. The

radian, which is the SI unit, is most frequently used in scientific or technical work and in

forming derived units. Use of the degree and its decimal fractions is permissible. Use

of the minute and second is discouraged except for specialized fields such as

cartography.

5.1.2 Solid angle

NOTE: No change in U.S. customary usage is required for solid angle units. The

steradian, which is the only unit commonly used to express solid angle, is an SI unit.

5.1.3 Length

ångström nanometer (nm) 0.1

fathom meter (m) 1.828 8

foot meter (m) 0.304 8

foot [U.S. survey] meter (m) 0.304 800 6

NOTE: In 1893 the U.S. foot was legally defined as 1200/3937 meters. In 1959 a

refinement was made to bring the foot into agreement with the definition used in other

countries, i.e. 0.3048 meters. At the same time it was decided that any data in feet derived

from and published as a result of geodetic surveys within the U.S. would remain with the old

standard, which is named the U.S. survey foot. The new length is shorter by exactly two

parts in a million. The five-digit multipliers given in this standard for acre and acre-foot are

correct for either the U.S. survey foot or the foot of 0.3048 meters exactly. Other lengths,

areas, and volumes are based on the foot of 0.3048 meters.

inch centimeter (cm) 2.54

millimeter (mm) 25.4

microinch micrometer (μm) 0.025 4

mil millimeter (mm) 0.025 4

micrometer (μm) 25.4
Fed-Std-376B

From To Multiply By

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yard meter (m) 0.914 4

5.1.3 Length (continued)

mile kilometer (km) 1.609 344

 nautical mile kilometer (km) 1.852

NOTE: The nautical mile is an accepted unit for use in navigation.

point millimeter (mm) 0.351 46

pica millimeter (mm) 4.217 5

5.1.4 Area

acre square meter (m2

) 4 046.9

hectare (ha) 0.404 69

NOTE: The hectare, equal to 10 000 m2, is accepted for use with SI.

circular mil square millimeter (mm2

) 0.000 506 708

square inch square centimeter (cm2

) 6.451 6

square millimeter (mm2

) 645.16

square foot square meter (m2

) 0.092 903 04

square yard square meter (m2

) 0.836 127 4

square mile square kilometer (km2

) 2.589 988

5.1.5 Volume

acre-foot cubic meter (m3

) 1 233.5

barrel, oil cubic meter (m3

) 0.158 987 3

 (42 U.S. gallons) liter (L) 158.987 3

NOTES: (1) The liter, equal to 0.001 m3, is accepted for use with SI. (2) A variety of barrel
Fed-Std-376B

From To Multiply By

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sizes have been used for other commodities.

cubic yard cubic meter (m3

) 0.764 555

5.1.5 Volume (continued)

cubic foot cubic meter (m3

) 0.028 316 85

liter (L) 28.316 85

board foot cubic meter (m3

) 0.002 359 737

register ton cubic meter (m3

) 2.831 685

NOTE: The register ton is a unit of volume used to express the capacity of a ship. For

example, a 20 000 ton freighter has a capacity of approximately 57 000 m3, measured in

accordance with established procedures.

bushel cubic meter (m3

) 0.035 239 07

NOTE: Agricultural products that are sold by the bushel in the United States are often sold by

weight in other countries. There can be a considerable variation in the weight per unit volume

due to differences in variety, size, or condition of the commodity, tightness of pack, degree to

which the container is heaped, etc. The following conversion factors are used by the U.S.

Department of Agriculture for statistical purposes:

Crop Weight per bushel (kg)

barley 21.8

corn, shelled 25.4

oats 14.5

potatoes, soybeans, wheat 27.2

gallon liter (L) 3.785 412

quart (liquid) liter (L) 0.946 352 9

pint (liquid) liter (L) 0.473 176 5

fluid ounce milliliter (mL) 29.573 53

NOTE: In the United States, the cup, tablespoon, and teaspoon are defined as 8, 1/2, and 1/6

fluid ounces, respectively. For practical usage the metric equivalents are 250 mL, 15 mL, and

5 mL.

cubic inch cubic centimeter (cm3

) 16.387 06
Fed-Std-376B

From To Multiply By

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5.1.6 Time

NOTE: No change in customary U.S. usage is required for time units. The second is the SI

unit of time, but the minute and hour, as well as the day, week, year, etc., are accepted

units.

5.1.7 Velocity

foot per second meter per second (m/s) 0.304 8

mile per hour kilometer per hour (km/h) 1.609 3

knot kilometer per hour (km/h) 1.852

NOTE: The knot, or nautical mile per hour, is an accepted unit for use in navigation.

5.1.8 Acceleration

inch per second squared meter per second squared (m/s2

) 0.025 4

foot per second squared meter per second squared (m/s2

) 0.304 8

standard acceleration of

 gravity (g) meter per second squared (m/s2

) 9.806 65

5.1.9 Flow rate

cubic foot per second cubic meter per second (m3

/s) 0.028 316 85

cubic foot per minute cubic meter per second (m3

/s) 0.000 471 947

liter per second (L/s) 0.471 947 4

cubic yard per minute liter per second (L/s) 12.742 58

gallon per minute liter per second (L/s) 0.063 090 2

gallon per day liter per day (L/d) 3.785 412
Fed-Std-376B

From To Multiply By

13

5.1.10 Fuel efficiency

mile per gallon kilometer per liter (km/L) 0.425 143 7

NOTE: To convert fuel efficiency in miles per gallon to fuel consumption in liters per

100 kilometers, use the formula: 235.2 / number of miles per gallon = number of liters per 100

kilometers

5.2 Quantities of Mechanics

5.2.1 Mass (weight)

NOTE: There is ambiguity in the use of the term "weight" to mean either force or mass. In

general usage, the term "weight" nearly always means mass and this is the meaning given the

term in U.S. laws and regulations. Where the term is so used, weight is expressed in

kilograms in SI. In many fields of science and technology the term "weight" is defined as the

force of gravity acting on an object, i.e., as the product of the mass of the object and the local

acceleration of gravity. Where weight is so defined, it is expressed in newtons in SI.

ton (long) kilogram (kg) 1 016.047

metric ton (t) 1.016 047

NOTE: The metric ton (referred to as "tonne" in many countries), equal to 1000 kg, is accepted

for use with SI.

ton (short) kilogram (kg) 907.184 74

metric ton (t) 0.907 184 7

slug kilogram (kg) 14.593 90

pound kilogram (kg) 0.453 592 37

ounce, troy gram (g) 31.103 48

ounce, avoirdupois gram (g) 28.349 52

grain milligram (mg) 64.798 91

5.2.2 Moment of mass

pound foot kilogram meter (kg⋅ m) 0.138 255 0
Fed-Std-376B

From To Multiply By

14

5.2.3 Density

ton (short) per cubic yard kilogram per cubic meter 1 186.553

 (kg/m3

)

metric ton per cubic meter (t/m3

) 1.186 553

pound per cubic foot kilogram per cubic meter (kg/m3

) 16.018 46

5.2.4 Concentration (mass)

pound per gallon gram per liter (g/L) 119.826 4

ounce per gallon gram per liter (g/L) 7.489 152

5.2.5 Momentum

pound foot per second kilogram meter per second 0.138 255 0

 (kg⋅ m/s)

5.2.6 Moment of inertia

pound square foot kilogram square meter (kg⋅ m2

) 0.042 140 11

5.2.7 Force

pound-force newton (N) 4.448 222

poundal newton (N) 0.138 255 0

5.2.8 Moment of force, torque

pound-force foot newton meter (N⋅ m) 1.355 818

pound-force inch newton meter (N⋅ m) 0.112 984 8

5.2.9 Pressure, stress

standard atmosphere kilopascal (kPa) 101.325

NOTE: The SI unit for pressure and stress is the pascal, which is equal to the newton per

square meter. This unit, its multiples, and submultiples are preferred for all applications.
Fed-Std-376B

From To Multiply By

15

5.2.9 Pressure, stress (continued)

bar kilopascal (kPa) 100

NOTE: The bar and its submultiples are accepted for limited use in meteorology only. It is

not accepted for use in the U.S. for other applications, e.g., as the unit of fluid pressure in

pipes and containers. The appropriate SI multiples, e.g., kilopascal or megapascal, should

be used instead.

millibar kilopascal (kPa) 0.1

pound-force kilopascal (kPa) 6.894 757

 per square inch

kilopound-force

 per square inch megapascal (MPa) 6.894 757

pound-force kilopascal (kPa) 0.047 880 26

 per square foot

inch of mercury kilopascal (kPa) 3.386 38

foot of water kilopascal (kPa) 2.988 98

inch of water kilopascal (kPa) 0.248 84

millimeter of mercury kilopascal (kPa) 0.133 322 4

NOTE: The actual pressure corresponding to the height of a vertical column of fluid

depends upon the local acceleration of gravity and the density of the fluid, which in turn

depends upon the temperature. The conversion factors given here are conventional values

adopted by the International Organization for Standardization (ISO).

torr pascal (Pa) 133.322 4

5.2.10 Viscosity (dynamic)

centipoise millipascal second (mPa⋅ s) 1

5.2.11 Viscosity (kinematic)

centistokes square millimeter 1

 per second (mm2

/s)
Fed-Std-376B

From To Multiply By

16

5.2.12 Energy, work, heat

kilowatthour megajoule (MJ) 3.6

NOTE: The kilowatthour is accepted as a unit of electrical energy only. The

SI unit of energy, the joule, which is equal to the newton meter or the watt

second, is recommended for all applications.

calorie joule (J) 4.184

 (as used in physics)

NOTE: The calorie listed here is the thermochemical calorie. Other values of the calorie

have been used.

calorie kilojoule (kJ) 4.184

 (as used in nutrition)

NOTE: The calorie used in nutrition is the same as the thermochemical kilocalorie. All use of

the calorie is deprecated.

Btu kilojoule (kJ) 1.055 056

NOTE: The British Thermal Unit (Btu) used in this standard is the International Table Btu

adopted by the Fifth International Conference on Properties of Steam, London, 1956.

therm (U.S.) megajoule (MJ) 105.480 4

horsepower hour megajoule (MJ) 2.684 520

foot pound-force joule (J) 1.355 818

 per second

5.2.13 Power

NOTE: Power is the rate of energy transfer. The SI unit for all forms of power—mechanical,

electrical, and heat flow rate—is the watt.

ton, refrigeration kilowatt (kW) 3.516 85

Btu per second kilowatt (kW) 1.055 056
Fed-Std-376B

From To Multiply By

17

Btu per hour watt (W) 0.293 071 1

5.2.13 Power (continued)

horsepower watt (W) 745.699 9

 (550 foot pounds-force

 per second)

horsepower, electric watt (W) 746

foot pound-force watt (W) 1.355 818

 per second

5.3 Quantities of Heat

5.3.1 Temperature

NOTE: The SI unit for customary temperature is the degree Celsius (°C). In inch-pound units

customary temperature is expressed in degrees Fahrenheit. The formula for converting

customary temperature is: tC = (tF - 32) /1.8

The SI unit for thermodynamic temperature TK is the kelvin (K). Celsius temperature is defined

by the equation: tC = TK - 273.15 K.

The inch-pound unit for thermodynamic temperature is the degree Rankine. The formula for

converting thermodynamic temperature is: TK = TR /1.8.

A temperature interval may be expressed in SI either in kelvins or in degrees Celsius, as

convenient. The formula for converting a temperature interval _t in degrees Fahrenheit into SI

is: _tK = _tC = _tF /1.8

5.3.2 Linear expansion coefficient

reciprocal degree reciprocal kelvin (K-1) or 1.8

 Fahrenheit reciprocal degree Celsius (°C-1)

5.3.3 Heat

NOTE: Heat is a form of energy. See 5.2.12

5.3.4 Heat flow rate

NOTE: Heat flow rate is a form of power. See 5.2.13
Fed-Std-376B

From To Multiply By

18

5.3.5 Thermal conductivity

Btu inch per hour square watt per meter kelvin 0.144 227 9

 foot degree Fahrenheit [W/(m⋅ K)]

5.3.6 Coefficient of heat transfer

Btu per hour square foot watt per square meter 5.678 263

 degree Fahrenheit kelvin [W/(m2

⋅ K)]

5.3.7 Heat capacity

Btu per degree Fahrenheit kilojoule per kelvin (kJ/K) 1.899 108

5.3.8 Specific heat capacity

Btu per pound kilojoule per kilogram 4.186 8

 degree Fahrenheit kelvin [kJ/(kg⋅ K)]

NOTE: The quantities 5.3.5 through 5.3.8 are defined in terms of temperature interval. 

Therefore K may be replaced by °C.

5.3.9 Entropy

Btu per degree Rankine kilojoule per kelvin (kJ/K) 1.899 108

5.3.10 Specific entropy

Btu per pound degree kilojoule per kilogram 4.186 8

 Rankine kelvin [kJ/(kg⋅ K)]

5.3.11 Specific internal energy

Btu per pound kilojoule per kilogram (kJ/kg) 2.326

5.4 Quantities of Electricity and Magnetism

NOTE: The common electrical units ampere (A), volt (V), ohm (Ω), siemens (S), coulomb

(C), farad (F), henry (H), weber (Wb), and tesla (T) are SI units that are already in use in the

United States. The various cgs units shall no longer be used.
Fed-Std-376B

From To Multiply By

19

5.4.1 Magnetic field strength

oersted ampere per meter (A/m) 79.577 47

5.4.2 Magnetic flux

maxwell nanoweber (nWb) 10

5.4.3 Magnetic flux density

gauss millitesla (mT) 0.1

5.4.4 Electric charge

ampere hour coulomb (C) 3 600

5.4.5 Resistivity

ohm circular mil nanoohm meter (nΩ⋅ m) 1.662 426

 per foot

5.4.6 Conductivity

mho per centimeter siemens per meter (S/m) 100

5.5 Quantities of Light and Related Electromagnetic Radiation

NOTE: No change in U.S. customary usage is required for the following quantities: radiant

intensity, watt per steradian (W/sr); radiance, watt per steradian square meter (W/[sr⋅ m

2

]);

irradiance, watt per square meter (W/m2); luminous intensity, candela (cd); luminous flux,

lumen (lm); and quantity of light, lumen second (lm⋅ s).

5.5.1 Wavelength

ångström nanometer (nm) 0.1

5.5.2 Luminance

lambert candela per square 3 183.099

 meter (cd/m2

)

candela per square inch candela per square 1 550.003
Fed-Std-376B

From To Multiply By

20

 meter (cd/m2

)

5.5.2 Luminance (continued)

footlambert candela per square 3.426 259

 meter (cd/m2

)

5.5.3 Luminous exitance

lumen per square foot lumen per square 10.763 91

 meter (lm/m2

)

5.5.4 Illuminance

footcandle lux (lx) 10.763 91

5.6 Quantities of Radiology

5.6.1 Activity (of a radionuclide)

curie megabecquerel (MBq) 37 000

5.6.2 Absorbed dose

rad gray (Gy) 0.01

centigray (cGy) 1

5.6.3 Dose equivalent

rem sievert (Sv) 0.01

millisievert (mSv) 10

millirem millisievert (mSv) 0.01

microsievert (μSv) 10

5.6.4 Exposure (x and gamma rays)

röentgen coulomb per 0.000 258

 kilogram (C/kg)
Fed. Std. 376B

21

BIBLIOGRAPHY

American National Standard for Metric Practice, ANSI/IEEE Std 268-1992, Institute of

Electrical and Electronics Engineers, Inc.

Requests for copies should be addressed to the Institute of Electrical and Electronics Engineers

(IEEE), Standards Department, 445 Hoes Lane, Piscataway, NJ 08855.

SI Units and Recommendations for the Use of their Multiples and of Certain Other Units, IS0

1000-1992

Requests for copies of this international standard, which is maintained by the International

Organization for Standardization (ISO), should be addressed to the American National Standards

Institute, 11 West 42nd St., New York, NY 10036.

Standard Practice for Use of the International System of Units (SI) (the Modernized Metric

System), ASTM E 380-91a

Requests for copies should be addressed to the American Society for Testing and Materials (ASTM),

1916 Race Street, Philadelphia, PA 19103.

Rules for SAE Use of SI (Metric) Units, SAE J916 (Rev. May 91)

Requests for copies should be addressed to Society of Automotive Engineers, Inc. (SAE), 400

Commonwealth Drive, Warrendale, PA 15096.

Metric Editorial Guide (fifth edition), ANMC-92-1

Requests for copies should be addressed to the American National Metric Council (ANMC),

Publication Services, 301 Warren Ave., Suite 217, Baltimore, MD 21230

Guide to the Use of the Metric System, 1992 edition

Requests for copies should be addressed to the U.S. Metric Association (USMA) 10245 Andasol Ave.,

Northridge, CA 91325-1504.

The International System of Units (SI), National Institute of Standards and Technology

(NIST) Special Publication 330 (1991 Edition)*

Guide for the Use of the International System of Units, The Modernized Metric System,

NIST Special Publication 811*

Interpretation of the SI and Metric Conversion Policy for Federal Agencies, NIST Special

Publication 814*, which includes:

Metric System of Measurement; Interpretation of the International System of Units for

the United States, (55 F.R. 52242, Dec. 20, 1990);

Metric Conversion Policy for Federal Agencies, 15 CFR Part 1170; and

Metric Usage in Federal Government Programs, Executive Order 12770 of July 25,

1991 (56 FR 35801, July 29, 1991)

*Requests for copies should be addressed to the National Technical Information Service, 5285 Port

Royal Rd., Springfield, VA 22161.

Fed. Std. 376B

23

Alphabetical Index

A

absorbed dose................................... 3, 20

acceleration ........................... 5, 12, 13, 15

acceleration of gravity........................... 12

acre ................................................... 9, 10

acre-foot ............................................ 9, 10

activity (of a radionuclide).................. 3, 20

ampere ........................................ 2, 18, 19

ampere hour .......................................... 19

ampere per meter.................................. 19

angle, plane..................................... 2, 4, 9

angle, solid .......................................... 2, 9

ångström........................................ 5, 9, 19

angular velocity........................................ 2

area ....................................................... 10

atmosphere........................................ 5, 14

B

bar ......................................................... 15

barrel, oil................................................ 10

becquerel................................................. 3

board foot .............................................. 11

Btu ................................................8, 16-18

Btu inch per hour square foot

 degree Fahrenheit ................................ 17

Btu per degree Fahrenheit..................... 18

Btu per degree Rankine......................... 18

Btu per hour..................................... 16, 18

Btu per hour square foot

 degree Fahrenheit ................................ 18

Btu per pound.................................... 8, 18

Btu per pound degree Fahrenheit.......... 18

Btu per pound degree Rankine.............. 18

Btu per second ...................................... 16

Bushel.................................................... 11

C

calorie................................................ 5, 16

candela.................................... 2, 5, 19, 20

candela per square inch ........................ 19

candela per square meter................ 19, 20

capacitance 3

Celsius temperature............................... 3, 17

centigray .................................................... 20

centimeter..................................... 5, 9-11, 19

centipoise .................................................. 15

centistokes................................................. 15

charge, electric ...................................... 3, 19

circular mil ........................................... 10, 19

concentration (mass) ................................. 14

conductance, electric ................................... 3

conductivity.......................................... 18, 19

conversion factors........................ 6, 8, 11, 15

coulomb ............................................ 3, 18-20

coulomb per kilogram ................................ 20

cubic centimeter ........................................ 11

cubic foot ....................................... 11, 12, 14

cubic foot per minute ................................. 12

cubic foot per second................................. 12

cubic inch................................................... 11

cubic meter..................................... 10-12, 14

cubic meter per second ............................. 12

cubic yard ...................................... 10, 12, 14

cubic yard per minute ................................ 12

cup............................................................. 11

curie........................................................... 20

current ......................................................... 2

D

day............................................................. 12

degree Celsius............................... 3, 4, 7, 17

degree Fahrenheit ................................. 1, 18

degree Rankine ................................... 17, 18

density ....................................... 3, 14, 15, 19

derived quantities......................................... 8

dose equivalent...................................... 3, 20

dose, absorbed...................................... 2, 20

E

electric charge ....................................... 3, 19

electricity and magnetism .................. 5, 8, 18

electromagnetic radiation........................... 19

electromotive force ...................................... 3
Fed. Std. 376B

24

energy............................................... 3, 16-18

entropy 18

exposure (x and gamma rays)............... 20

F

farad .................................................. 3, 18

fathom ..................................................... 9

field strength, magnetic ......................... 18

flow rate........................................... 12, 17

fluid ounce ............................................. 11

flux density, magnetic ........................ 3, 19

flux, luminous..................................... 3, 19

flux, magnetic .................................... 3, 19

foot .......................................................... 9

foot per second................................ 12, 14

foot per second squared........................ 12

footcandle.............................................. 20

footlambert............................................. 20

foot of water........................................... 15

foot pound-force per second............ 16, 17

force .........................................3, 5, 13-17

frequency................................................. 3

fuel consumption ................................... 13

fuel efficiency......................................... 13

G

gallon............................................1, 11-14

gallon per day ........................................ 12

gallon per minute ................................... 12

gauss................................................. 5, 19

grain ...................................................... 13

gram ............................................ 5, 13, 14

gram per liter ......................................... 14

gray ................................................... 3, 20

H

heat ..........................................3, 8, 16-18

heat capacity ......................................... 18

heat flow rate................................... 16, 17

heat transfer .......................................... 18

hectare........................................... 2, 8, 10

henry ................................................. 3, 18

hertz ........................................................ 3

horsepower.................................. 5, 16, 17

horsepower, electric17

horsepower hour........................................ 16

hour ............................................ 4, 12, 16-19

I

illuminance............................................. 3, 20

inch.......................... 6-7, 9-12, 14, 15, 17, 19

inch of mercury .......................................... 15

inch of water .............................................. 15

inch per second squared ........................... 12

inch-pound..................................... 1, 6, 8, 17

inductance ................................................... 3

inertia, moment of...................................... 14

intensity, luminous ................................. 2, 19

intensity, radiant ........................................ 19

irradiance................................................... 19

J

joule....................................................... 3, 16

K

kelvin ............................................... 2, 17, 18

kilocalorie................................................... 16

kilogram ....................... 2, 5, 8, 13, 14, 18, 20

kilogram meter..................................... 13, 14

kilogram meter per second ........................ 14

kilogram per cubic meter ........................... 14

kilogram square meter............................... 14

kilojoule................................................ 16, 18

kilojoule per kelvin ..................................... 18

kilojoule per kilogram................................. 18

kilojoule per kilogram kelvin....................... 18

kilometer.................................... 4, 10, 12, 13

kilometer per hour...................................... 12

kilometer per liter....................................... 13

kilopascal............................................. 14, 15

kilopound-force per square inch ................ 15

kilowatt....................................................... 16

kilowatthour ............................................... 16

knot............................................................ 12
Fed. Std. 376B

25

L

lambert............................................... 5, 19

length..............................................2, 7-10

light.................................................... 8, 19

linear expansion coefficient ................... 17

liter........................................ 2, 4, 8, 10-14

liter per day............................................ 12

liter per second...................................... 12

lumen........................................... 3, 19, 20

lumen per square foot............................ 20

lumen per square meter ........................ 20

lumen second ........................................ 19

luminance ........................................ 19, 20

luminous exitance.................................. 20

luminous flux...................................... 3, 19

luminous intensity .............................. 2, 19

lux...................................................... 3, 20

M

magnetic field strength .......................... 19

magnetic flux ..................................... 3, 19

magnetic flux density ......................... 3, 19

mass............................................ 2, 13, 14

mass, moment of................................... 13

maxwell.............................................. 5, 19

mechanics ..................................... 5, 8, 13

megabecquerel...................................... 20

megajoule.............................................. 16

megapascal ........................................... 15

meter ...............................2, 5, 9-14, 16-20

meter per second......................... 2, 12, 14

meter per second squared.................... 12

metric ton................................. 2, 8, 13, 14

metric ton per cubic meter..................... 14

mho ................................................... 5, 19

mho per centimeter................................ 19

microinch ................................................. 9

micrometer........................................... 5, 9

micron...................................................... 5

microsievert ........................................... 20

mil................................................ 9, 10, 19

mil, circular ...................................... 10, 19

mile.............................................. 4, 10, 12

mile, nautical................................ 4, 10, 12

mile per gallon ....................................... 13

mile per hour.......................................... 12

millibar ................................................... 15

milligram 13

milliliter....................................................... 11

millimeter ................................. 3, 5, 9, 10, 15

millimeter of mercury ............................. 5, 15

millipascal second...................................... 15

millirem ...................................................... 20

millisievert.................................................. 20

millitesla..................................................... 19

mole............................................................. 2

moment of force......................................... 14

moment of inertia....................................... 14

moment of mass ........................................ 13

momentum................................................. 14

N

nanometer ......................................... 5, 9, 19

nanoohm meter ......................................... 19

nanoweber................................................. 19

nautical mile..................................... 4, 10, 12

newton............................................. 3, 14, 16

newton meter....................................... 14, 16

O

oersted................................................... 5, 18

ohm.................................................. 3, 18, 19

ohm circular mil per foot ............................ 19

ounce............................................. 11, 13, 14

ounce, avoirdupois..................................... 13

ounce, fluid ................................................ 11

ounce per gallon ........................................ 14

ounce, troy................................................. 13

P

pascal .......................................................... 3

pica............................................................ 10

pint............................................................. 11

plane angle .......................................... 2, 4, 9

point........................................................... 10

poise............................................................ 5

potential difference ...................................... 3

pound..................................... 1, 8, 13, 14, 18
Fed. Std. 376B

26

pound foot............................................ 13, 14

pound foot per second............................... 14

pound-force 14-17

pound-force foot .................................... 14

pound-force inch.................................... 14

pound-force per square foot .................. 15

pound-force per square inch.................. 15

pound per cubic foot .............................. 14

pound per gallon.................................... 14

pound square foot.................................. 14

poundal.................................................. 14

power........................................... 3, 16, 17

pressure....................................... 3, 14, 15

Q

quantity of electricity ................................ 3

quantity of heat........................................ 3

Quantities of Electricity .......................... 18

Quantities of heat ................................. 17

Quantities of Light.................................. 19

Quantities of Magnetism........................ 18

Quantities of Mechanics ........................ 13

Quantities of Radiology.......................... 19

Quantities of Space ................................. 9

Quantities of time..................................... 9

quart ...................................................... 11

R

rad ................................................. 2, 5, 20

radian................................................... 2, 9

radian per second.................................... 2

radiance................................................. 19

radiant intensity ..................................... 19

radiation, electromagnetic...................... 19

radionuclide, activity of ...................... 2, 20

radiology ............................................ 8, 20

reciprocal degree Celsius ...................... 17

reciprocal degree Fahrenheit................. 17

reciprocal kelvin..................................... 17

register ton............................................. 10

rem ........................................................ 20

resistivity................................................ 19

röentgen ................................................ 20

rounding............................................... 6, 7

S

second 2, 5, 8, 12, 14-17

SI units...................................... 1-5, 8, 18, 21

siemens ....................................... 3, 5, 18, 19

siemens per meter..................................... 19

sievert.................................................... 3, 20

significant digits ........................................ 6-8

slug............................................................ 13

solid angle ............................................... 2, 9

space and time ........................................ 8, 9

specific entropy.......................................... 18

specific heat capacity................................. 18

specific internal energy .............................. 18

square centimeter...................................... 10

square foot......................... 10, 14, 15, 18, 20

square inch .................................... 10, 15, 19

square kilometer ........................................ 10

square meter ........................... 10, 14, 18, 19

square mile ................................................ 10

square millimeter ................................. 10, 15

square millimeter per second..................... 15

square yard................................................ 10

standard acceleration of gravity................ 12

standard atmosphere............................. 5, 14

steradian............................................ 2, 9, 19

stokes .......................................................... 5

stress ............................................... 3, 14, 15

supplemental lists ........................................ 8

survey foot ................................................... 9

T

tablespoon ................................................. 11

teaspoon.................................................... 11

temperature ................................... 2, 3, 7, 17

temperature interval............................. 17, 18

tesla....................................................... 3, 18

therm ......................................................... 16

thermal conductivity................................... 18

thermodynamic temperature.................. 2, 17

time............................................ 2, 4, 8, 9, 12

ton.................................... 2, 8, 11, 13, 14, 16

ton (long) ................................................... 13

ton, metric.................................... 2, 8, 13, 14

ton, refrigeration ........................................ 16
Fed. Std. 376B

27

ton (short) ............................................ 13, 14

ton (short) per cubic yard........................... 14

torque ........................................................ 14

torr......................................................... 5, 15

V

velocity............................................... 2, 12

viscosity (dynamic) ................................ 15

viscosity (kinematic) .............................. 15

volt..................................................... 3, 18

volume............................................. 10, 11

W

watt...........................................3, 4, 16-19

watt per meter kelvin ............................. 17

watt per square meter...................... 18, 19

watt per square meter kelvin.................. 18

watt per steradian .................................. 19

watt per steradian square meter............ 19

wavelength ............................................ 19

weber................................................. 3, 18

weight ...................................... 2, 8, 11, 13

work......................................... 3, 9, 16, 17

Y

yard ....................................... 1, 10, 12, 14

year ....................................................... 12