The National Conference on Weights and Measures (NCWM) and the Office of Weights and Measures of the National Institute of Standards and Technology (NIST) publish NIST Handbook 130, Uniform Laws and Regulations in the Areas of Legal Metrology and Engine Fuel Quality.
The Handbook, as such, is not a law. But it’s designed to be used as a model for US state weights and measures laws, and many states use the Handbook for their state laws. The extracts here reflect the 2010 edition of the Handbook, which you can download from NIST. We’ve also included links below to specific sections of the handbook.
Note: Although the links to Handbook 130 above and below retrieve the 2009 edition, it’s the same as the 2010 edition of Handbook 130 except for two sections that were amended. For the 2010 amendments, see the amendment to section 2.1 (which also explains why no 2010 edition was published) and the amendment to section 2.13. However, neither of those amendments affects the sections discussed on this page.
If you’re curious about a particular state’s use of the Uniform Laws and Regulations, refer to the table in section II, Uniformity of Laws and Regulations (PDF).
The Handbook consists of several uniform laws and regulations, and you can view a complete list in the table of contents (PDF). Of primary interest here are three:
- Uniform Weights and Measures Law
- Uniform Packaging and Labeling Regulation (UPLR)
- Uniform Unit Pricing Regulation (UPR)
Uniform Weights and Measures Law
The Uniform Weights and Measures Law (PDF) is designed to be the primary weights and measures law of a state.
Among other things, it recognizes the International System (SI) and the customary system for use in the state, and adopts the various uniform laws and regulations, including those mentioned below (a state may, of course, pick and choose which ones it incorporates into its laws).
Uniform Packaging and Labeling Regulation (UPLR)
The Uniform Packaging and Labeling Regulation (PDF), incorporated by reference in the Uniform Weights and Measures Law mentioned above, is similar to the Fair Packaging and Labeling Act plus the regulations implementing the FPLA. Read the Background section of the UPLR (p. 3 in the PDF, p. 55 of the Handbook) for more on its relationship to the FPLA.
The UPLR goes into great detail on labeling requirements, some of which apply to all labels and others that apply to specific products or package shapes. Because the topic at hand is metric measurement, we’ll stick to the metric-related sections here.
Customary, metric, or both?
In general, the UPLR permits metric-only labels as well as labels with dual units. But note that the UPLR does not supersede federal laws, so it applies only to products not covered by the FPLA and similar federal laws, which, at present, generally do not permit metric-only labels.
Three sections of the UPLR define the unit requirements for labels.
- First, §6.1 states that labels must (in general) include both metric and non-metric units.
- Next, §11.32 lists situations where metric units are not required, i.e., where solely non-metric labels are legal. In general, this list parallels the list in federal laws.
- Finally, §11.33 goes on to say that, in spite of the aforementioned rules, any label that does include metric units may omit the non-metric units, except for situations covered by federal laws that say otherwise.
Following are those three sections from the UPLR:
6.1. General. — The International System of Units (SI), known as the metric system and the inch-pound system of weights and measures are recognized as proper systems to be used in the declaration of quantity. Effective , appropriate units of both systems shall be presented in a declaration of quantity except as specified in Section 11.32, SI Units, Exemptions for Consumer Commodities and Section 11.33, Inch-Pound Units, Exemptions — Consumer Commodities. (Amended 1985, 1990, 1993, and 1999)
NOTE 3: Packages subject to this Section and/or the Federal Fair Packaging and Labeling Act shall be labeled in units of the International System of Units (SI) and the inch-pound system of measure effective , [except for seed (see Section 10.10. Packaged Seed) and camera film and recording tape (see Section 11.22. Camera Film, Video Recording Tape, Audio Recording Tape and Other Image and Audio Recording Media Intended for Retail Sale and Consumer Use), and as specified in Section 11.32. SI Units, Exemptions — Consumer Commodities]. SI units may appear first. (Added 1982) (Amended 1990 and 1993)
11.32. SI Units, Exemptions — Consumer Commodities. — The requirements for statements of quantity in SI units (except for those in Section 10.10. Packaged Seed and Section 11.22. Camera Film, Video Recording Tape, Audio Recording Tape and Other Image and Audio Recording Media Intended for Retail Sale and Consumer Use) in Section 6. Declaration of Quantity: Consumer Packages shall not apply to:
(a) Foods packaged at the retail store level,
(b) Random weight packages (see Sections 2.4. and 11.1.),
(c) Package labels printed before ,
(d) Meat and poultry products subject to the Federal Meat or Poultry Products Inspection Acts,
(e) Tobacco or tobacco products,
(f) Any beverage subject to the Federal Alcohol Administration Act,
(g) Any product subject to the Federal Insecticide, Fungicide, and Rodenticide Act,
(h) Drugs and cosmetics subject to the Federal Food, Drug and Cosmetic Act,
(i) Nutrition labeling information.
11.33. Inch-Pound Units, Exemptions — Consumer Commodities. — The requirements for statements of quantity in inch-pound units shall not apply to packages that bear appropriate SI units. This exemption does not apply to foods, drugs, or cosmetics or to packages subject to regulation by the Federal Trade Commission, meat and poultry products subject to the Federal Meat or Poultry Products Inspection Acts, and tobacco or tobacco products. (Added 1999)
Form of metric measurements
Several sections detail the format of the metric measurement on a label, and which unit to use. Here are some of the relevant sections of the UPLR.
6.2. Largest Whole Unit. — Where this regulation requires that the quantity declaration be in terms of the largest whole unit, the declaration shall, with respect to a particular package, be in terms of the largest whole unit of weight or measure with any remainder expressed (following the requirements of § 6.5.2. (a) and § 6.11. Fractions):
(a) SI Units, in decimal fractions of such largest whole unit.
6.5. SI Units: Mass, Measure — A declaration of quantity:
(a) in units of mass shall be the kilogram, gram, or milligram;
(b) in units of liquid measure shall be the liter or milliliter and shall express the volume at 20 °C, except in the case of petroleum products or distilled spirits, for which the declaration shall express the volume at 15.6 °C, 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 °C;
(c) in units of linear measure shall be the meter, centimeter, or millimeter;
(d) in units of area measure shall be the square meter, square decimeters, square centimeter, or square millimeter;
(e) in units of volume other than liquid measure shall be the liter and milliliter, except that the units cubic meter and cubic centimeter shall be used only when specifically designated as a method of sale;
(f) Rule of 1000. — The selected multiple or submultiple prefixes for SI units shall result in numerical values between 1 and 1000. This rule allows centimeters or millimeters to be used where a length declaration is less than 100 centimeters. For example: 500 g not 0.5 kg; 1.96 kg not 1960 g; or 750 mL, not 0.75 L, or, 750 mm or 75 cm, not 0.75 m;
(g) SI declarations should be shown in three digits except where the quantity is below 100 grams, milliliters, centimeters, square centimeters, or cubic centimeters, where it may be shown in two digits. In either case, any final zero appearing to the right of the decimal point need not be shown.
(h) The declaration of net quantity of contents shall not be expressed in mixed units. For example: 1.5 kg, not 1 kg 500 g.
6.5.1. Symbols. — Any of the following symbols for SI units, and none other, may be employed in the quantity statement on a package of commodity:
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 milliliter mL or ml cubic decimeter dm3 square centimeter cm2 square decimeter dm2 micrometer µm microgram µg or mcg (a) 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 form. Adding “s” to an SI symbol to express the plural of the symbol is prohibited.
(b) The “L” symbol and the “mL” symbol are preferred; however, the “l” symbol for liter and “ml” symbol for milliliter are permitted.
6.5.2. Fractions and Prefixes. —
(a) Fractions: An SI statement in a declaration of net quantity of contents of any consumer commodity may contain only decimal fractions.
(b) Prefixes:The following chart indicates SI prefixes that may be used on a broad range of consumer commodity labels to form multiples and submultiples of SI units:
Prefix Symbol Multiplying Factor* kilo- k × 103 deca-** da × 10 deci-** d × 10-1 centi-*** c × 10-2 milli- m × 10-3 micro-**** µ × 10-6 * 102 = 100; 103 = 1000; 10-1 = 0.1; 10-2 = 0.01
Thus, 2 kg = 2 × 1000 g = 2000 g and 3 cm = 3 × 0.01 m = 0.03 m
** Not permitted on food labels.
*** Should only be used with “meter”.
**** Shall only be used for measurements less than 1 mm.
6.6. Prescribed Units, SI.
6.6.1. Less than 1 Meter, 1 Square Meter, 1 Kilogram, 1 Cubic Meter, or 1 Liter. – The declaration of quantity shall be expressed as follows:
(a) length measure of less than 1 meter: in centimeters or millimeters;
(b) area measure of less than 1 square meter: in square decimeters and decimal fractions of a square decimeter or in square centimeters and decimal fractions of a square centimeter;
(c) mass of less than 1 kilogram: in grams and decimal fractions of a gram, but if less than 1 gram, then in milligrams;
(d) liquid or dry measure of less than 1 liter: in milliliters;
(e) cubic measure less than 1 cubic meter: in cubic centimeters or cubic decimeters (liters) [See § 10.11. Cubic Measure in Compressed Form];
provided, the quantity declaration appearing on a random mass package may be expressed in units of decimal fractions of the largest appropriate unit, the fraction being carried out to not more than three decimal places.
6.6.2. One Meter, 1 Square Meter, 1 Kilogram, 1 Liter, 1 Cubic Meter, or More. –In the case of:
(a) length measure of 1 meter or more: in meters and decimal fractions to not more than three places;
(b) area measure of 1 square meter or more: in square meters and decimal fractions to not more than three places;
(c) mass of 1 kilogram or more: in kilograms and decimal fractions to not more than three places;
(d) liquid or dry measure of 1 liter or more: in liters and decimal fractions to not more than three places;
(e) cubic measure of 1 cubic meter or more: in cubic meters and decimal fractions to not more than three places (See § 10.11. Cubic Measure in Compressed Form).
Section 6.9, not reproduced here, gives the rules for bidimensional quantities, explaining when to show the area, the length and width, or both.
The rules quoted above refer to consumer packages. Section 7 gives the rules for nonconsumer packages, which are similar but less detailed. Sections 10 and 11 give details for various products that have special rules.
Uniform Unit Pricing Regulation (UPR)
The Uniform Unit Pricing Regulation (PDF) covers unit-pricing labels. In general, unit prices must be provided unless the package is smaller than 28 g (1 oz) or 29 mL (1 fl oz), or costs 50¢ or less, or there’s only one brand in one size on sale at a particular retail establishment.
If the unit price is $1 or more, it must be rounded to the nearest cent. For unit prices below $1, a retailer may choose to round to the nearest cent or to the nearest tenth of a cent (but must do so consistently).
The choice of units for unit prices come from one of five categories, depending on how the product’s net contents are measured:
| How measured? | Then use these metric units |
or these customary units |
|---|---|---|
| Weight | per kilogram per 100 grams |
per pound per ounce |
| Dry measure or volume |
per litre per 100 millilitres |
per dry quart per dry pint |
| Liquid volume | per litre per 100 millilitres |
per gallon per quart per pint per fluid ounce |
| Count | per unit or multiple units | |
| Area | per square metre per square decimetre per square centimetre |
per square yard per square foot per square inch |
Where more than one choice is shown, the retailer may use any of them, and may use metric, non-metric, or both, provided the pricing units are consistent for a given product in different brands and sizes.
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