1. in units of mass shall be in terms of the kilogram, gram, or milligram;
2. in units of liquid measure shall be in terms of the liter or milliliter, and shall express the volume at 20 ^oC, except in the case of petroleum products or distilled spirits, for which the declaration shall express the volume at 15.6 ^oC, and except also in the case of a commodity that is normally sold and consumed while frozen, for which the declaration shall express the volume at the frozen temperature, and except also in the case of malt beverages or a commodity that must be maintained in the refrigerated state, for which the declaration shall express the volume at 4 ^oC;
3. in units of linear measure shall be in terms of the meter, centimeter, or millimeter (except that, micrometer is used when the declaration is less than 1 mm);
4. in units of area measure, shall be in terms of the square meter, square decimeters, square centimeter, or square millimeter;
5. in units of volume other than liquid measure, shall be in terms of the liter and milliliter, except that the terms cubic meter and cubic centimeter shall be used only when specifically designated as a method of sale;

centimeter	cm	cubic meter	m³
cubic centimeter	cm³	kilogram	kg
meter	m	gram	g
milligram	mg	millimeter	mm
liter	L or l	square meter	m²
mililiter	mL or ml	cubic decimeter	dm³
square centimeter	cm²	square decimeter	dm²
micrometer	µm

1. Capitalization, Plurals -- Symbols, except for liter, are not capitalized unless the unit is derived from a proper name. Periods shall not be used after the symbol. Symbols shall always be written in the singular formit is not acceptable to add "s" to an SI symbol to express the plural of the symbol.
2. Symbols for Liter, Milliliter -- The "L" symbol and the "mL" symbol are preferred; however, the "l" symbol for liter and "ml" symbol for milliliter are permitted.

Prefix	Symbol	Multiplying Factor*
kilo-	k	x 103
deca-**	da	x 10
deci-	d	x 10-1
centi-***	c	x 10-2
milli-	m	x 10-3
micro-****	µ	x 10-6
*102 =100; 103 =1000; 10-1 = 0.1; 10-2 =0.01 Thus, 2 kg=22 x 1000 g=2000 g and 3 cm=3 x 0.01 m=0.03 m **Not permitted on food labels. ***Should be used only with "Meter." ****Shall only be used for measurements less than 1 mm.

Less than 1 meter, 1 square meter, 1 kilogram, 1 cubic meter, or 1 liter shall be expressed as follows:

1. length measure of less than 1 meter: in centimeters or millimeters;
2. area measure of less than 1 square meter: in square decimeters and fractions of a square decimeter or in square centimeters and fractions of a square centimeter;
3. mass of less than 1 kilogram: in grams and fractions of a gram, but if less than 1 gram, then in milligrams;
4. liquid or dry measure of less than 1 liter: in milliliters;
5. cubic measure less than 1 cubic meter: in cubic centimeters or cubic decimeters (liters);

provided, the quantity declaration appearing on a random mass package may be expressed in terms of decimal fractions of the largest appropriate unit, the fraction being carried out to not more than three decimal places.

One meter, 1 square meter, 1 kilogram, 1 cubic meter, or 1 liter or more -- In the case of:

1. length measure of 1 meter or more: in meters and decimal fractions to not more than three places;
2. area measure of 1 square meter or more: in square meters and decimal fractions to not more than three places;
3. mass of 1 kilogram or more: in kilograms and decimal fractions to not more than three places;
4. liquid or dry measure of 1 liter or more: in liters and decimal fractions to not more than three places.
5. cubic measure of 1 cubic meter or more: in cubic meters and decimal fractions to not more than three places.

Bidimensional commodities -- For bidimensional commodities (including rolltype commodities), the SI quantity declaration shall be expressed:

1. if the area is less than 929 cm² (1 sq ft), in terms of length and width (expressed in the largest whole unit);
2. if the area is at least 929 cm² (1 sq ft) but less than 37.1 dm² (4 sq ft), in terms of area (expressed in the largest whole unit) followed by a declaration of length and width in terms of the largest whole unit, provided:
   1. for bidimensional commodities having a width of 10 cm (4 in) or less, the declaration of net quantity shall be expressed in terms of width and length only;
   2. commodities consisting of usable individual units (except rolltype commodities with individual usable units created by perforations, for which see UPLR § 6.10. Count: Ply.) require a declaration of unit area but not a declaration of total area of all such units.

3. if the area is 37.1 dm² (4 sq ft) or more, in terms of area (expressed in terms of the largest whole unit) followed by a declaration of the length and width, in terms of the largest whole unit; provided no declaration of area is required for a bidimensional commodity with a width of 10 cm (4 in) or less.
4. no declaration in square units is required for commodities for which the length and width measurements are critical in terms of end use (such as wallpaper border) if such commodities clearly present the length and width measurements on the label.

•	Rounding -- In all conversions for the purpose of showing an equivalent SI or inch-pound quantity to a rounded inch-pound or SI quantity, or in calculated values to be declared in the net quantity statement, the number of significant digits retained must be such that accuracy is neither sacrificed nor exaggerated. Conversions, the proper use of significant digits, and rounding must be based on the packer's knowledge of the accuracy of the original measurement that is being converted. In no case shall rounded net contents declarations overstate a quantity; the packer may round converted values down to avoid overstating the net contents. (See the attached Appendixes A & B from the UPLR.) Note: When as a result of rounding SI or customary inch-pound declarations calculated based on the conversion factors in Appendix A, the resulting declarations are not exact, the largest number will be used for enforcement purposes to determine whether a package contains at least the declared amount of product.
•	Minimum Height of Numbers and Letters -- The height of any letter or number in the required quantity declaration shall be not less than that shown in Table 1 below, with respect to the area of the panel, and the height of each number of a common fraction shall meet one-half the minimum height standards. When upper and lower case, or all lowercase letters are used in SI symbols, it is the uppercase "L," lowercase "d," or their equivalent in the print or type that shall meet the minimum height requirement. However, no letter shall be less than 1.6 mm (1/16 in) in height. Other letters and exponents must be presented in the same type style and in proportion to the type size used. Table 1. Minimum Height of Numbers and Letters Area of principal display panel Minimum height of numbers and letters Minimum height: label information blown, formed, or molded on surface on container <= 32 cm² (5 in²) 1.6 mm (1/16 in) 3.2 mm (1/8 in) > 32 cm² (5 in²) <=161 cm² (25 in²) 3.2 mm (1/8 in) 4.8 mm (3/16 in) > 161 cm² (25 in²) <=645 cm² (100 in²) 4.8 mm (3/16 in) 6.4 mm (1/4 in) > 645 cm² (100 in²) <=2581 cm2 (400 in²) 6.4 mm (1/4 in) 7.9 mm (5/16 in) > 2581 cm² (400 in²) 12.7 mm (1/2 in) 14.3 mm (9/16 in) Symbols:<= means less than or equal to; < means less than; > means greater than Note: The type size requirements specified in this table do not apply to the "e" mark.
•	For Complete Information on Packaging and Labeling Requirements: See National Institute of Standards and Technology (NIST) Handbook 130, Uniform Laws and Regulations, or the applicable Federal, State, or local regulations for additional packaging and labeling requirements. Copies of Handbook 130 may be purchased from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402 (Tele. no.: 202-783-3238). Copies may also be obtained as a benefit of membership in the NCWM.

Conversion - To convert an inch-pound quantity to an SI quantity, multiply the appropriate conversion factor in Table 1 in Appendix A by the inch-pound unit and round according to the following rules.

Rounding and Significant Digits - It is the packager's responsibility to round converted values appropriately and select the appropriate number of significant digits to use in quantity declaration. [These rounding rules are for converting quantity determinations on packages and do not apply to digital scales that automatically round indications to the nearest indicated value.] Conversions, the proper use of significant digits, and rounding must be based on the packer's knowledge of the accuracy of the original measurement that is being converted. For example; if a package is labeled 453.59 g (1 lb), the packer is implying that the package declaration is accurate within ± 0.005 g (or ± 5 mg). For liquid volume measure, a label declaration of 473 mL (16 fl oz) implies that the package declaration is accurate to within ± 0.5 mL (0.01 fl oz). The requirements of § 6.13. Rounding apply to all quantity declarations that are derived from converted values:

6.13. Rounding. -- In all conversions for the purpose of showing an equivalent SI or inch-pound quantity to a rounded inch-pound or SI quantity, or in calculated values to be declared in the net quantity statement, the number of significant digits retained must be such that accuracy is neither sacrificed nor exaggerated. Conversions, the proper use of significant digits, and rounding must be based on the packer's knowledge of the accuracy of the original measurement that is being converted. In no case shall rounded net contents declarations overstate a quantity; the packer may round converted values down to avoid overstating the net contents.

Note: When as a result of rounding SI or customary inch-pound declarations calculated based on the conversion factors in Appendix A, the resulting declarations are not exact, the largest number will be used for enforcement purposes to determine whether a package contains at least the declared amount of product.

Do not round conversion factors or any other quantity used or determined in the calculation; only round the final quantity to the number of significant digits needed to maintain the accuracy of the original quantity. Use the rounding rules presented below in Table 1 as guidance to round the final result. In general, quantity declarations on consumer commodities should only be shown to two or three significant digits (for example, 453 g or 85 g). Any final zeros to the right of the decimal point need not be expressed. The inch-pound and SI declarations of quantity must be accurate and equivalent to each other. For example, a package bearing a net weight declaration of 2 lb (32 oz) must also include an SI declaration of 907 g.

Table 1. Rounding Rules
When The First Digit Dropped is:	The Last Digit Retained is:	Examples
Less than 5	Unchanged	2.44 to 2.4 2.429 to 2.4
More than 5, or 5 followed by at least 1 digit other than 0	Increased by 1	2.46 to 2.5 2.51 to 2.5
5 followed by zeros	Unchanged if Even, or increased by 1 if Odd	2.450 to 2.4 2.550 to 2.6

1. When the first digit discarded is less than five, the last digit retained should not be changed. For example, if the quantity 984.3 is to be declared to three significant digits, the figure 3 to the right of the decimal point must be discarded since it is less than 5 and the last digit to be retained (the figure "4") will remain unchanged. The rounded number will read 984. The same rationale applies to numbers declared to two significant digits (for example 68.4 and 7.34); again the final digit is dropped and the last digit retained remains unchanged so that the "rounded-off" numbers become 68 and 7.3 respectively.
2. When the first digit to be discarded is greater than five, or it is a five followed by at least one digit other than zero, the last digit to be retained should be increased by one unit.

   Examples:

   984.7 becomes 985
   984.51 becomes 985
   6.86 becomes 6.9
   6.88 becomes 6.9

3. When the first digit to be discarded is exactly five, followed only by zeros, the final digit to be retained should be rounded up if it is an odd number (1,3,5,7, or 9), but no adjustment should be made if it is an even number (2,4,6, or 8).

   Examples:

   984.50 becomes 984
   985.50 becomes 986
   68.50 becomes 68
   7.450 becomes 7.4
   7.550 becomes 7.6

   *Note: See additional examples on page 9.

Additional Advice on Rounding and Significant Digits

1. These rules require the packer to use good judgement in making decisions on how to round and the number of significant digits to use in quantity declarations. Rounding should always be done in one step; for example, if 16.94647 g has to be rounded to 3 significant digits, it should be rounded to 16.9 g, not 16.9465, then to 16.946, then to 16.95 which would then round to 17.0 g (See rounding rules above).
2. Do not use rounded SI values to calculate quantities. For example, using 1 inch = 25.4 mm, rounded to 25 mm, should not be multiplied by 2 to determine the SI equivalent for 2 inches. The SI equivalent for 2 in is determined by multiplying 2 in x 25.4 mm = 50.8 mm, then rounding to 51 mm.
3. If a dimension given as 8 feet is valid to the nearest 1/10 inch, consider it to mean 96.0 inches and treat it as having 3 significant digits. The rounded dimension would then be 2.44 m instead of 2.4 m.
4. Conversions using a multiple digit conversion factor usually give a product with more digits than the original quantity. The final product should contain no more significant digits than are contained in the number with the fewest significant digits used in the conversion. For example, the area of a sheet of paper is determined on a calculator by multiplying 1.25 cm (length) x 1.5 cm (width) = 1.875 cm². The product given to 4 significant digits on the calculator cannot be any more accurate than 2 significant digits (the number of significant digits in 1.5 cm), so the area should be declared as 1.9 cm².
5. Packagers of consumer commodities should be aware that when a converted value is rounded up, there may be a need to (1) increase the package contents and/or, (2) select a converted value that does not exaggerate the precision of the quantity or overstate the net contents. For example, under the rules above, a net weight declaration of 16 oz (453.592 37 g) would be rounded up 0.4 g to 454 g for 3 significant digits. Inspections by weights and measures officials are typically conducted using devices with a resolution of 0.5 g or less. If the packer does not address this possibility, some lots of commodities may pass when the inch-pound declaration is tested, but fail when the SI declaration is verified.

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For technical questions concerning the Metric Program, contact us:

Laws & Metric Group, Weights and Measures Division, NIST, 100 Bureau Drive, Stop 2600, Gaithersburg, MD 20899-2600
Phone: (301) 975-4004, Fax: (301) 926-0647, Email: TheSI@nist.gov

Date created: April 23, 1999
Date Last Modified: June 16, 2004

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