United States

Department of

Agriculture

Agricultural 

Marketing

Service

Fruit and

Vegetable

Programs

Fresh

Products

Branch

United States Standards

for Grades of

Potatoes

Effective June 3, 2011
1

United States Standards for Grades of Potatoes 1

Grades

51.1540 [Reserved].

51.1541 U.S. No. 1.

51.1542 U.S. Commercial.

51.1543 U.S. No. 2.

51.1544 [Reserved].

Size

51.1545 Size.

Tolerances

51.1546 Tolerances.

Application of Tolerances

51.1547 Application of tolerances.

Samples for Grade and Size Determination

51.1548 Samples for grade and size determination.

Skinning

51.1549 Skinning.

Definitions

51.1550 Similar varietal characteristics.

51.1551 Firm.

51.1552 Clean.

51.1553 Fairly clean.

51.1554 Mature.

51.1555 Fairly well matured.

51.1556 Well shaped.

51.1557 Fairly well shaped.

51.1558 Seriously misshapen.

51.1559 [Removed and Reserved].

51.1560 Damage.

51.1561 Serious damage.

51.1562 Freezing.

51.1563 Soft rot or wet breakdown.

51.1564 External defects.

51.1565 Internal defects.

Metric Conversion Table

51.1566 Metric conversion table.

 

1

Packing of the product in conformity with requirements of these standards shall not excuse failure to comply with the provisions of 

the Federal Food and Drug Cosmetic Act or with applicable State laws and regulations.
2

Grades

§51.1540 [Reserved].

§51.1541 U.S. No. 1. 

"U.S. No. 1" consists of potatoes which meet the following requirements: 

(a) Similar varietal characteristics, except when designated as a mixed or specialty pack; 

(b) Firm; 

(c) Fairly clean;2

(d) Fairly well shaped; 

 

(e) Free from: 

(1) Freezing; 

(2) Blackheart; 

(3) Late blight, southern bacterial wilt and ring rot; and, 

(4) Soft rot and wet breakdown. 

(f) Free from damage by any other cause. See §§51.1564 and 51.1565. 

(g) Size. Not less than 1-7/8 inches in diameter, unless otherwise specified in connection with 

the grade. 

(h) For tolerances see §51.1546. 

§51.1542 U.S. Commercial. 

"U.S. Commercial" consists of potatoes which meet the requirements of U.S. No. 1 grade except 

for the following: 

(a) Free from serious damage caused by: 

(1) Dirt or other foreign matter; 

(2) Russet scab; and, 

(3) Rhizoctonia. 

(b) Increased tolerances for defects specified in §51.1546. 

§51.1543 U.S. No. 2. 

"U.S. No. 2" consists of potatoes which meet the following requirements: 

(a) Similar varietal characteristics, except when designated as a mixed or specialty pack; 

(b) Not seriously misshapen; 

(c) Free from: 

(1) Freezing; 

(2) Blackheart; 

(3) Late blight, southern bacterial wilt and ring rot; and, 

(4) Soft rot and wet breakdown. 

(d) Free from serious damage by any other cause. See §§51.1564 and 51.1565. 

(e) Size. Not less than 1-1/2 inches in diameter, unless otherwise specified in connection with 

the grade. 

(f) For tolerances see §51.1546. 

§51.1544 [Reserved].

 

2

Potatoes in containers bearing official State Seed Certification Tags and Seals are not required to be fairly clean but shall be free 

from damage by dirt.
3

Size 

§51.1545 Size. 

(a) The minimum size, or minimum and maximum sizes may be specified in connection with the 

grade in terms of diameter or weight of the individual potato, or in accordance with one of the 

size designations in Table I or Table II: Provided, That sizes so specified shall not be in conflict 

with the basic size requirements for the grade. 

(b) When size is designated as shown in Table II, the corresponding weight ranges shall apply. 

These size designations may be applied to potatoes packed in any size container: Provided, That 

the weight ranges are within the limits specified.
4

Table I

Size designation

Minimum

diameter1 or

weight

Maximum

diameter1 or

weight

Inches Ounces Inches Ounces

Creamer................ 3/4 (

3

) 1-5/8 (

3

)

Chef.................. 2-3/4 8 4-1/2 28

Size A2................. 1-7/8 (

3

) (

3

) (

3

)

Size B.................. 1-1/2 (

3

) 2-1/4 (

3

)

Small................... 1-3/4 (

3

) 2-1/2 6

Medium.................. 2-1/4 5 3-1/4 10

Large................... 3 10 4-1/2 28

1

Diameter means the greatest dimension at right angles to the longitudinal axis, without regard to the position of the 

stem end.

2

In addition to the minimum size specified, a lot of potatoes designated as Size A shall contain at least 40 percent of 

potatoes which are 2-1/2 inches in diameter or larger or 6 ounces in weight or larger. 3

No requirement.

Table II

[Ounces]

Size designation

Minimum

weight

Maximum

weight

Under 50....................... 15 ...........

50............................. 12 19

60............................. 10 16

70............................. 9 15

80............................. 8 13

90............................. 7 12

100............................ 6 10

110............................ 5 9

120............................ 4 8

130............................ 4 8

140............................ 4 8

Over 140....................... 4 8
5

Tolerances 

§51.1546 Tolerances. 

To allow for variations incident to proper grading and handling in each of the foregoing grades, 

the following tolerances by weight or equivalent basis, are provided as specified.

(a) For defects -- (1) U.S. No. 1. (i) At Shipping Point: A total of 8 percent for potatoes in any 

lot which fail to meet the requirements for the grade: Provided, That included in this tolerance 

not more than the following percentages shall be allowed for the defects listed: 

(A) 5 percent for external defects;

(B) 5 percent for internal defects; and

(C) Not more than a total of 1 percent for potatoes which are frozen or affected by soft rot or wet 

breakdown. See §51.1547.

(ii) En route or at Destination: A total of 10 percent for potatoes in any lot which fail to meet 

the requirements for the grade: Provided, That included in this tolerance not more a total of 8 

percent shall be allowed for permanent defects: And provided further, the following 

percentages shall be allowed for the defects listed:

(A) 7 percent for external defects, including therein not more than 5 percent for permanent 

external defects;

(B) 7 percent for internal defects, including therein not more than 5 percent for permanent 

internal defects; and

(C) Not more than a total of 2 percent for potatoes which are frozen or affected by soft rot or wet 

breakdown. See §51.1547.

(2) U.S. Commercial. A total of 20 percent for potatoes in any lot which fail to meet the 

requirements for the grade: Provided, That included in this tolerance not more than the 

following percentages shall be allowed for the defects listed:

(i) 10 percent for potatoes which fail to meet the requirements for U.S. No. 2 grade, including 

therein not more than:

(ii) 6 percent for external defects; 

(iii) 6 percent for internal defects; and

(iv) Not more than a total of 1 percent for potatoes which are frozen or affected by soft rot or wet 

breakdown. See §51.1547. 

(3) U.S. No. 2. (i) At Shipping Point: A total of 10 percent for potatoes in any lot which fail to 

meet the requirements for the grade: Provided, That included in this tolerance not more than the 

following percentages shall be allowed for the defects listed: 

(A) 6 percent for external defects;

(B) 6 percent for internal defects; and

(C) Not more than a total of 1 percent for potatoes which are frozen or affected by soft rot or wet 

breakdown. See §51.1547.

(ii) En route or at Destination: A total of 12 percent for potatoes in any lot which fail to meet 

the requirements for the grade: Provided, That included in this tolerance not more than 10 

percent shall be allowed for permanent defects: And provided further, the following 

percentages shall be allowed for the defects listed: 

(A) 8 percent for external defects, including therein not more than 6 percent for permanent 

external defects; 

(B) 8 percent for internal defects, including therein not more than 6 percent for permanent 

internal defects; and
6

(C) Not more than a total of 2 percent for potatoes which are frozen or affected by soft rot or wet 

breakdown. See §51.1547.

(b) For off-size. (1) Not more than 3 percent of the potatoes in any lot may be smaller than the 

required or specified minimum size except that a tolerance of 5 percent shall be allowed for 

potatoes packed to meet a minimum size of 2-1/4 inches or larger in diameter or 5 ounces or 

more in weight. In addition, not more than 10 percent may be larger than any required or 

specified maximum size. See §51.1547. 

(2) When a percentage of the potatoes is specified to be of a certain size and larger, individual 

samples shall have not less than one-half of the percentage specified: Provided, That the 

average for the entire lot is not less than the percentage specified. 

Application of Tolerances 

§51.1547 Application of tolerances. 

Individual samples shall have not more than double the tolerances specified, except that at least 

one defective and one off-size potato may be permitted in any sample: Provided, That en route 

or at destination one-tenth of the samples may contain three times the tolerance permitted for 

potatoes which are frozen or affected by soft rot or wet breakdown. And provided further,

That the averages for the entire lot are within the tolerances specified for the grade.

Samples for Grade and Size Determination 

§51.1548 Samples for grade and size determination. 

Individual samples shall consist of at least 20 pounds. When individual packages contain at least 

20 pounds, each individual sample is drawn from one package; when packages contain less than 

20 pounds, a sufficient number of adjoining packages are opened to provide at least a 20-pound 

sample. The number of such individual samples drawn for grade and size determination will 

vary with the size of the lot. 

Skinning 

§51.1549 Skinning. 

(a) The following definitions provide a basis for describing lots of potatoes as to the degree of 

skinning whenever description may be appropriate: 

(1) "Practically no skinning" means that not more than 5 percent of the potatoes in the lot have 

more than one-tenth of the skin missing or "feathered;" 

(2) "Slightly skinned" means that not more than 10 percent of the potatoes in the lot have more 

than one-fourth of the skin missing or "feathered;" 

(3) "Moderately skinned" means that not more than 10 percent of the potatoes in the lot have 

more than one-half of the skin missing or "feathered;" and 

(4) "Badly skinned" means that more than 10 percent of the potatoes in the lot have more than 

one-half of the skin missing or "feathered." 

Definitions 

§51.1550 Similar varietal characteristics. 

"Similar varietal characteristics" means that the potatoes in any lot have the same general shape, 

color and character of skin, and color of flesh. 

§51.1551 Firm. 

"Firm" means that the potato is not shriveled or flabby. 

§51.1552 Clean.

"Clean" means that at least 90 percent of the potatoes in any lot are practically free from dirt or 

staining and practically no loose dirt or other foreign matter is present in the container. 
7

§51.1553 Fairly clean. 

"Fairly clean" means that at least 90 percent of the potatoes in any lot are reasonably free from 

dirt or staining and not more than a slight amount of loose dirt or foreign matter is present in the 

container.

§51.1554 Mature. 

"Mature" means that the skins of the potatoes are generally firmly set and not more than 5 

percent of the potatoes in the lot have more than one-tenth of the skin missing or "feathered."

§51.1555 Fairly well matured. 

"Fairly well matured" means that the skins of the potatoes are generally fairly firmly set and not 

more than 10 percent of the potatoes in the lot have more than one-fourth of the skin missing or 

"feathered." 

§51.1556 Well shaped. 

"Well shaped" means that the potato has the normal shape for the variety.

§51.1557 Fairly well shaped. 

"Fairly well shaped" means that the potato is not materially pointed, dumbbell-shaped or 

otherwise materially deformed. 

§51.1558 Seriously misshapen.

"Seriously misshapen" means that the potato is seriously pointed, dumbbell-shaped or otherwise 

badly deformed. 

§51.1559 [Removed and Reserved].

§51.1560 Damage.

"Damage" means any defect, or any combination of defects, which materially detracts from the 

edible or marketing quality, or the internal or external appearance of the potato, or any external 

defect which cannot be removed without a loss of more than 5 percent of the total weight of the 

potato. See Tables III, IV, V, and VI in §51.1564 and Table VII in §51.1565.

§51.1561 Serious damage.

"Serious damage" means any defect, or any combination of defects, which seriously detracts 

from the edible or marketing quality, or the internal or external appearance of the potato, or any 

external defect which cannot be removed without a loss of more than 10 percent of the total 

weight of the potato. See Tables III, IV, V, and VI in §51.1564 and Table VII in §51.1565.

§51.1562 Freezing.

"Freezing" means that the potato is frozen or shows evidence of having been frozen. 

§51.1563 Soft rot or wet breakdown.

"Soft rot or wet breakdown" means any soft, mushy, or leaky condition of the tissue such as 

slimy soft rot, leak, or wet breakdown following freezing injury. 

§51.1564 External defects. 

"External defects" are defects which can be detected externally. However, cutting may be 

required to determine the extent of the injury. Some external defects are listed in Tables III, IV, 

V, and VI.
8

Table III - External Defects

Defects Damage Serious Damage1

Air Cracks When removal causes a loss of more than 

5 percent of the total weight of the potato 

or when the air crack(s) affects more than 

1/3 the length or diameter of the potato 

(whichever is greater) in the aggregate. 

When removal causes a loss of 

more than 10 percent of the total 

weight of the potato or when the air 

crack(s) affects more than 3/4 the 

length or diameter of the potato 

(whichever is greater) in the 

aggregate.

Artificial Coloring When unsightly or when concealing any 

defect causing damage or when 

penetrating the flesh and removal causes 

loss of more than 5 percent of total 

weight of potato.

When concealing a serious defect or 

when penetrating into the flesh and 

removal causes loss of more than 10 

percent of total weight of potato.

Bruises (Not including 

pressure bruise and sunken 

discolored areas)

When removal causes a loss of more than 

5 percent of the total weight of the potato 

or when the area affected is more than 5 

percent of the surface in the aggregate 

(i.e. 3/4 inch on a 2-1/2 inch or 6 oz. 

potato). Correspondingly lesser or 

greater areas in smaller or larger 

potatoes.

When removal causes a loss of 

more than 10 percent of the total 

weight of the potato or when the 

area affected is more than 10 

percent of the surface in the 

aggregate (i.e. 1-1/4 inches on a 

2-1/2 inch or 6 oz. potato). 

Correspondingly lesser or greater 

areas in smaller or larger potatoes.

Cuts When one smooth cut affects more than 5 

percent of the surface area.

Cut(s) that affect more than 10 

percent of the surface area in the 

aggregate or when a single side cut 

extends beyond 1/2 the length of the 

potato.

Dirt When materially detracting from the 

appearance of the potato.

When seriously detracting from the 

appearance of the potato.

Elephant Hide When affecting over 10 percent of the 

surface area of the potato. 

When affecting over 25 percent of 

the surface area.

Enlarged Lenticels When materially detracting from the 

appearance of the potato.

When seriously detracting from the 

appearance of the potato.

External Discoloration (Areas 

that are light tan or lighter in 

color and blends should be 

ignored.)

When more than 30 percent of the 

surface is affected by light tan or light 

brown colors which do not blend or when 

more than 15 percent of the surface is 

affected by colors darker than light tan or 

light brown. 

When more than 60 percent of the 

surface is affected by light tan or 

light brown colors which do not 

blend or when more than 30 percent 

of the surface is affected by colors 

darker than light tan or light brown. 
9

Defects Damage Serious Damage1

Flattened or Depressed 

Areas/Pressure Bruises

When removal of underlying discolored 

flesh causes a loss of more than 5 percent 

of the total weight of the potato or when 

the flattened or depressed area(s) covers 

more surface area than allowed in Table 

IV. (See Table IV.)

When removal of underlying 

discolored flesh causes a loss of 

more than 10 percent of the weight 

of the potato or when the flattened 

depressed area(s) covers more 

surface area than allowed in the 

Table IV. (See Table IV.) 

Flea Beetle Injury When materially detracting from the 

appearance or when removal causes a 

loss of more than 5 percent of the total 

weight of the potato or when the area 

affected is more than 5 percent of the 

surface in the aggregate.

When seriously detracting from the 

appearance of the potato or when 

removal causes a loss of more than 

10 percent of the weight of the 

potato or when the area affected is 

more than 10 percent of the surface 

in the aggregate.

Greening When removal causes a loss of more than 

5 percent of the total weight of the potato 

or when green color affects more than 25 

percent of the surface in the aggregate. 

When removal causes a loss of 

more than 10 percent of the weight 

of the potato or when green color 

affects more than 50 percent of the 

surface in the aggregate.

Growth Cracks When the growth crack(s) affects more 

than 1/2 the length of the potato in the 

aggregate on round varieties or more 

than 1/3 the length in the aggregate on 

long varieties; or, when the depth is 

greater than that as outlined in Table V. 

(See Table V.)

When the growth crack(s) affects 

more than 3/4 the length of the 

potato in the aggregate or when the 

depth is greater than that as outlined 

in Table V. (See Table V.)

Grub Damage When removal causes a loss of more than 

5 percent of the total weight of the potato 

or when affecting more than 5 percent of 

the surface area (i.e. more than 3/4 inch 

on a 2-1/2 inch or 6 ounce potato). 

Correspondingly lesser or greater areas in 

smaller or larger potatoes.

When removal causes a loss of 

more than 10 percent of the total 

weight of the potato or when 

affecting more than 10 percent of 

the surface area (i.e. more than 

1-1/4 inch on a 2-1/2 inch or 6 

ounce potato). Correspondingly 

lesser or greater areas in smaller or 

larger potatoes.

Insects or Worms (See Serious Damage.) When present inside the potato.

Nematode (Root Knot) When removal causes loss of more than 5 

percent of total weight of potato. 

When removal causes loss of more 

than 10 percent of total weight of 

potato. 

Rhizoctonia When affecting more than 15 percent of 

the surface in the aggregate. 

When affecting more than 50 

percent of the surface in the 

aggregate. 
10

Defects Damage Serious Damage1

Rodent or Bird Damage When removal causes a loss of more 

than 5 percent of the total weight of the 

potato or when affecting more than 5 

percent of the surface area (i.e. more 

than 3/4 inch on a 2-1/2 inch or 6 ounce 

potato). Correspondingly lesser or 

greater areas in smaller or larger 

potatoes.

When removal causes a loss of more 

than 10 percent of the total weight of 

the potato or when affecting more than 

10 percent of the surface area (i.e. more 

than 1-1/4 inch on a 2-1/2 inch or 6 

ounce potato). Correspondingly lesser 

or greater areas in smaller or larger 

potatoes.

Russeting (On Non Russet 

Type)

When more than 50 percent of the 

surface is affected in the aggregate. 

N/A

Scab, Pitted When removal causes a loss of more 

than 5 percent of the total weight of the 

potato or when scab affects an 

aggregate area of more than 1/2 inch. 

(Based on a potato 2-1/2 inches in 

diameter or 6 oz. in weight.) 

Correspondingly lesser or greater areas 

in smaller or larger potatoes.

When the removal causes a loss of more 

than 10 percent of the total weight of 

the potato or when scab affects an 

aggregate area of more than 1 inch. 

(Based on a potato 2-1/2 inches in 

diameter or 6 oz. in weight.) 

Correspondingly lesser or greater areas 

in smaller or larger potatoes.

Scab, Russet Smooth and affecting more than 1/3 of 

the surface or rough russet scab which 

affects more than 10 percent of the 

surface in the aggregate. 

Rough and affecting more than 25 

percent of the surface in the aggregate.

Scab, Surface When more than 5 percent of the 

surface in the aggregate is affected.

When more than 25 percent of the 

surface in the aggregate is affected.

Second Growth When materially detracting from the 

appearance of the potato. 

When seriously detracting from the 

appearance of the potato. 

Silver Scurf When affecting more than 50 percent of 

the surface area of the potato.

When its severity causes a wrinkling of 

the skin over more than 50 percent of 

the surface.

Sprouts When more than 5 percent of the 

potatoes in any lot have any sprout

more than 1/4 inch in length at shipping 

point, more than 1/2 inch in length at 

destination; or have numerous 

individual and/or clusters of sprouts 

which materially detract from the 

appearance of the potato.

When more than 10 percent of the 

potatoes in any lot have any sprout 

more than 1/2 inch in length at shipping 

point, more than 1 inch in length at 

destination; or have numerous 

individual and/or clusters of sprouts 

which seriously detract from the 

appearance of the potato. Serious 

damage by sprouts shall only be scored 

against the U.S. Commercial and 

U.S. No. 2 grades.
11

Defects Damage Serious Damage1

Sunburn When removal causes loss of more than 

5 percent of total weight of potato.

When removal causes loss of more than 

10 percent of total weight of potato.

Sunken Discolored Areas SEE TABLE VI SEE TABLE VI

Surface Cracks (Areas affected

by fine net-like cracking should 

be ignored.)

When smooth shallow cracking affects more 

than 1/3 of the surface or when rough deep 

cracking affects more than 5 percent of the 

surface.

When rough deep cracking affects more 

than 10 percent of the surface.

Wireworm or Grass Damage When affecting the flesh of the potato and 

removal causes loss of more than 5 percent 

of total weight of potato.

When affecting the flesh of the potato and 

removal causes loss of more than 10 percent 

of total weight of potato.

1

The following defects are considered serious damage when present in any degree: 1. Freezing. 2. Late blight. 3. Ring rot. 

4. Southern bacterial wilt. 5. Soft rot. 6. Wet breakdown.

Table IV

Flattened or Depressed Areas - Pressure Bruises Maximum Area Allowed

Diameter Weight No. 1 (aggregate 

area)

No. 2

(aggregate area)

Potato is: Potato is: Not more than: Not more than:

Less than 2 in. Less than 4 oz. 1/2 in. 1 in.

2 to 2-1/2 in. 4 to 6 oz. 1 in. 1-1/2 in.

More than 2-1/2 to 3 in. More than 6 to 8 oz. 1-1/4 in. 1-3/4 in.

More than 3 to 3-1/2 in. More than 8 to 14 oz. 1-1/2 in. 1-7/8 in.

More than 3-1/2 to 4 in. More than 14 to 20 oz. 1-3/4 in. 2 in.

More than 4 to 4-1/2 in. More than 20 to 28 oz. 2 in. 2-1/4 in.

More than 4-1/2 to 5 in. More than 28 to 36 oz. 2-1/4 in. 2-3/4 in.

More than 5 in. More than 36 oz. 2-1/2 in. 3-1/4 in.
12

Table V

Depth Allowed For Growth Cracks

Diameter Weight No. 1 (Depth) No. 2 (Depth)

Potato is: Potato is: Not more than: Not more than:

Less than 2 in. Less than 4 oz. 1/8 in. 1/4 in.

2 to 2-1/2 in. 4 oz. to 6 oz. 1/4in. 3/8 in.

More than 2-1/2 to 3 in. More than 6 oz. to 8 oz. 3/8 in. 1/2 in.

More than 3 in. More than 8 oz. 1/2 in. 5/8 in.

Table VI

Sunken Discolored Areas Maximum Area Allowed

Diameter Weight

No. 1

(aggregate area)

No. 2

(aggregate area)

Potato is: Potato is: Not more than: Not more than:

Less than 2 in. Less than 4 oz. 3/8 in. 3/4 in.

2 to 2-1/2 in. 4 to 6 oz. 3/4 in. 1 in.

More than 2-1/2 to 3 in. More than 6 to 8 oz. 1 in. 1-1/4 in.

More than 3 to 3-1/2 in. More than 8 to 14 oz. 1-1/4 in. 1-1/2 in.

More than 3-1/2 to 4 in. More than 14 to 20 oz. 1-1/2 in. 1-3/4 in.

More than 4 to 4-1/2 in. More than 20 to 28 oz. 1-3/4 in. 2 in.

More than 4-1/2 to 5 in. More than 28 to 36 oz. 2 in. 2-1/4 in.

More than 5 in. More than 36 oz. 2-1/4 in. 2-1/2 in.
13

§51.1565 Internal defects. 

"Internal defects" are defects which cannot be detected without cutting the potato. Some internal 

defects are listed in Table VII. 

Table VII -- Internal Defects

Defects Damage

Maximum Allowed

Serious Damage

Maximum Allowed

Occurring outside of or not entirely confined to the vascular ring

Ingrown Sprouts, Internal Black 

Spot, Internal Discoloration, 

Vascular Browning, Fusarium Wilt, 

Net Necrosis, Other Necrosis, Stem 

End Browning

5% waste 10% waste

Internal Black Spot. When the spot(s) are darker than 

the official color chip (POT-CC-2) 

after removing 5 percent of the 

total weight of the potato. 

When the spot(s) are darker than 

the official color chip (POT-CC-2) 

after removing 10 percent of the 

total weight of the potato. 

Occurring entirely within the vascular ring

Hollow Heart or Hollow Heart with 

Discoloration

Area affected not to exceed that of 

a circle 1/2 inch in diameter in a 

potato 2-1/2 inches in diameter or 6 

ounces in weight.1

Area affected not to exceed that of 

a circle 3/4 inch in diameter in a 

potato 2-1/2 inches in diameter or 6 

ounces in weight.1

Light Brown Discoloration

(Brown Center)

Area affected not to exceed that of 

a circle 1/2 inch in diameter in a 

potato 2-1/2 inches in diameter or 6 

ounces in weight.1

Area affected not to exceed that of 

a circle 3/4 inch in diameter in a 

potato 2-1/2 inches in diameter or 6 

ounces in weight.1

Internal Brown Spot and Similar 

Discoloration (Heat Necrosis)

Not more than the equivalent of 3 

scattered spots 1/8 inch in diameter 

in a potato 2-1/2 inches in diameter 

or 6 ounces in weight.1

Not more than the equivalent of 6 

scattered spots 1/8 inch in diameter 

in a potato 2-1/2 inches in diameter 

or 6 ounces in weight.1

1

Note: Correspondingly lesser or greater areas in smaller or larger potatoes.
14

Metric Conversion Table

§51.1566 Metric conversion table.

Ounces Grams

1 equals......................................................28.35

4 equals....................................................113.40

5 equals....................................................141.75

6 equals....................................................170.10

7 equals....................................................198.45

8 equals....................................................226.80

9 equals....................................................255.15

10 equals..................................................283.50

12 equals..................................................340.20

14 equals..................................................396.90

16 equals..................................................453.60

18 equals..................................................510.30

19 equals..................................................538.60

20 equals..................................................567.00

Inches Millimeters (mm)

1/8 equals.....................................................3.2

1/4 equals.....................................................6.4

1/2 equals...................................................12.7

3/4 equals...................................................19.1

1 equals......................................................25.4

1-1/2 equals ...............................................38.1

2 equals......................................................50.8

2-1/2 equals ...............................................63.5

3 equals......................................................76.2

3-1/2 equals ...............................................88.9

4 equals....................................................101.6

4-1/2 equals .............................................114.3