Handbook 133 – 2023 Introduction

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Introduction

A. Source

The information and procedures in this handbook comprise all of those adopted by the National Conference 

on Weights and Measures, Inc. (NCWM). Contact NCWM at:

1135 M Street, Suite 100 Phone: (402) 434-4880 E-mail: info@ncwm.com

Lincoln, NE 68508 Fax: (402) 434-4878 URL: www.ncwm.com

The NCWM is supported by the National Institute of Standards and Technology (NIST), which provides 

its Executive Secretary and publishes its documents. NIST also develops technical publications for use by 

weights and measures agencies; these publications may subsequently be endorsed or adopted by the NCWM 

or its members.

This handbook is recommended by NCWM for adoption by states when reviewing or amending their 

official laws and regulations on testing the net contents of packaged goods. A similar recommendation is 

made with regard to the local jurisdictions within a state in the absence of the promulgation of such laws 

and regulations at the state level.

(Amended 2019)

B. Purpose

This handbook has been prepared as a procedural guide for the compliance testing of net content statements 

on packaged goods. Compliance testing of packaged goods is the determination of the conformance of the 

results of the packaging, distribution, and retailing process (the packages) to specific legal requirements for 

net content declarations. This handbook has been developed primarily for the use of government officials. 

However, commercial and industrial establishments packaging, distributing, and selling commodities will 

find this handbook useful.

In conducting compliance testing, the conversion of quantity values from one measurement system to 

another (e.g., from the metric system to the U.S. customary system) should be handled with careful regard 

to the implied correspondence between the accuracy of the data and the number of digits displayed. In all 

conversions, the number of significant digits retained should ensure that accuracy is neither sacrificed nor 

exaggerated. For this 2020 edition of NIST Handbook 133, “Checking the Net Content of Packaged 

Goods” all dimensions for test procedures, devices, or environments have been rounded to two significant 

digits (e.g., 2.5 cm to 1.0 in) or to a precision level applicable to the test equipment (e.g., 200 kPa for 25 psi 

and 35 MPa for 5000 psi).

C. Amendments

Amendments to NIST Handbook 133 are deliberated and developed by NCWM’s Committee on Laws and 

Regulations before presentation to the general membership for a vote. In some instances, amendments that 

significantly affect other NIST Handbooks may be processed jointly by two or more committees.

Amendments to the handbooks are made in accordance with NCWM procedures and policies. The process 

begins at the regional weights and measures association meetings in the fall of each year and is culminated 

at the NCWM Annual Meeting in July. After passing through one or more of the regional associations, the 

proposed amendment is placed on the agenda of the appropriate NCWM committee for consideration at the 
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NCWM’s Interim Meeting in January. After final deliberation and development by the committee, the 

amendment may be presented to the membership for a vote at the NCWM Annual Meeting in July. The 

NCWM policy provides for exceptions to the process to accommodate urgent or priority items. NIST staff 

provides technical assistance and advice throughout the process.

The policy is available on the NCWM website at www.ncwm.com. For information on the regional weights 

and measures associations, visit www.ncwm.com/other-links. 

D. Revisions to the Handbook 

NIST publishes a new edition of this handbook after significant changes are made. If NIST determines that 

amendments made by NCWM were minor or editorial in nature an annual publication will not be published. 

Instead, NIST will issue a notice that the current edition is still valid and will publish a list of the changes 

on the NIST website. 

E. Annotation

Beginning in 1971, amendments or additions to sections in the handbook are annotated at the end of each 

section (e.g., “Amended 1982”) as a service to those states that are planning to update their own laws or 

regulations. The references to each revision and the year will enable government officials and industry 

members to trace the rationale for the changes by referring to the “Report of the XXX National Conference 

on Weights and Measures (also known as the NCWM Annual Report) for the year indicated and make 

decisions regarding adoptions and amendments to their laws and regulations. 

F. Effective Enforcement Dates of Regulations

Unless otherwise specified, new or amended sections are intended to become effective and subject to 

enforcement on January 1 of the year following adoption by NCWM.

G. Section References

In most references made to specific sections or subsections in this handbook, the word “Section” followed 

by the section number is used.

H. The International System of Units

The “International System of Units,” “SI,” or “SI Units” means the modernized metric system as established 

in 1960 by the General Conference on Weights and Measures (CGPM). In 1988, Congress amended the 

Metric Conversion Act of 1975 (see Section 5164 of Public Law 100-418) to declare that it is the policy of 

the United States to designate the metric system of measurement as the preferred measurement system for 

U.S. trade and commerce, and it further defined “the metric system of measurement” to be the International 

System as established by the CGPM and as interpreted or modified for the United States by the Secretary 

of Commerce. (see Metric Conversion Law 15 U.S.C. 205; NIST Special Publication (SP) 330, “The 

International System of Units (SI); NIST SP 814, “Guide for the Use of the International System of Units 

(SI); Interpretation of the International System of Units [the Metric System of Measurement] for the United 

States in the “Federal Register” of May 16, 2008, [“Federal Register” Vol. 73, No. 96] or subsequent 

revisions). In 1992, Congress amended the Federal Fair Packaging and Labeling Act (FPLA) to require 

certain consumer commodities to include the appropriate SI units along with the customary inch-pound 

units in their quantity statements.

(Amended 2019)
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I. “Mass” and “Weight” [NOTE 1, page 3]

The mass of an object is a measure of the object’s inertial property or the amount of matter it contains. The 

weight of an object is a measure of the force exerted on the object by gravity or the force needed to support 

it. The pull of gravity on the earth gives an object a downward acceleration of about 9.8 m/s2

. In trade and 

commerce and everyday use, the term “weight” is often used as a synonym for “mass.” The “net mass” or 

“net weight” declared on a label indicates that the package contains a specific amount of commodity 

exclusive of wrapping materials. The use of the term “mass” is predominant throughout the world and is 

becoming increasingly common in the United States.

J. Use of the Terms “Mass” and “Weight” [NOTE 1, page 3]

When used in this handbook, the term “weight” means “mass.” The term “weight” appears when U.S. 

customary units are cited or when both inch-pound and SI units are included in a requirement. The terms 

“mass” or “masses” are used when only SI units are cited in a requirement. The following note appears 

where the term “weight” is first used in a law or regulation.

NOTE 1: When used in this law (or regulation), the term “weight” means “mass.” (see paragraphs 

I. “Mass” and Weight and J. Use of the Terms “Mass” and “Weight” in the Introduction section of NIST 

Handbook 133 for an explanation of these terms.)

(Introduction added 2015)
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