Appendix C of 

NIST Handbook 44, 

Specifications, Tolerances, and Other Technical Requirements 

General Tables of Units of Measurement 

These tables have been prepared for the benefit of those requiring tables of units for occasional ready reference. In Section 4 of this appendix, the tables are carried out to a large number of decimal places and exact values are indicated by underlining. In most of the other tables only a limited number of decimal places are given, thus making the tables better adapted to the average user.


Tables of Metric Units of Measurement Tables of U.S. Units of Measurement Notes on British Units of Measurement Tables of Units of Measurement U.S. Units and Metric Units Tables of Equivalents Links to the Metric Program Conversion Sites  
1. TABLES OF METRIC UNITS OF MEASUREMENT  
In the metric system of measurement, designations of multiples and subdivisions of any unit may be arrived at by combining with the name of the unit the prefixes deka, hecto, and kilo meaning, respectively, 10, 100, and 1000, and deci, centi, and milli, meaning, respectively, onetenth, onehundredth, and onethousandth. In some of the following metric tables, some such multiples and subdivisions have not been included for the reason that these have little, if any currency in actual usage. In certain cases, particularly in scientific usage, it becomes convenient to provide for multiples larger than 1 000 and for subdivisions smaller than onethousandth. Accordingly, the following prefixes have been introduced and these are now generally recognized:














2. TABLES OF U.S. UNITS OF MEASUREMENT^{2}  
In these tables where foot or mile is underlined, it is survey foot or U.S. statute mile rather than international foot or mile that is meant.
























3. NOTES ON BRITISH UNITS OF MEASUREMENT  
In Great Britain, the yard, the avoirdupois pound, the troy pound, and the apothecaries pound areidentical with the units of the same names used in the United States. The tables of British linear measure, troy mass, and apothecaries mass are the same as the corresponding United States tables, except for the British spelling "drachm" in the table of apothecaries mass. The table of British avoirdupois mass is the same as the United States table up to 1 pound; above that point the table reads:




The present British gallon and bushelknown as the "Imperial gallon" and "Imperial bushel" are, respectively, about 20 percent and 3 percent larger than the United States gallon and bushel. The Imperial gallon is defined as the volume of 10 avoirdupois pounds of water under specified conditions, and the Imperial bushel is defined as 8 Imperial gallons. Also, the subdivision of the Imperial gallon as presented in the table of British apothecaries fluid measure differs in two important respects from the corresponding United States subdivision, in that the Imperial gallon is divided into 160 fluid ounces (whereas the United States gallon is divided into 128 fluid ounces), and a "fluid scruple" is included. The full table of British measures of capacity (which are used alike for liquid and for dry commodities) is as follows




The full table of British apothecaries measure is as follows




4. TABLES OF UNITS OF MEASUREMENT Units of Length  International Measure^{8}
Units of Area  International Measure^{9}
Units of Area  Survey Measure9
Units of Volume
Units of Capacity or Volume  Dry Volume Measure
Units of Capacity or Volume  Liquid Volume Measure
Units of Mass Not Less Than Avoirdupois Ounces
Units of Mass Not Greater Than Pounds or Kilograms


5. TABLES OF EQUIVALENTS  
In these tables it is necessary to differentiate between the "international foot" and the "survey foot;" the survey foot is underlined. When the name of a unit is enclosed in brackets (thus, [1 hand] . . . ), this indicates (1) that the unit is not in general current use in the United States, or (2) that the unit is believed to be based on "custom and usage" rather than on formal authoritative definition. Equivalents involving decimals are, in most instances, rounded off to the third decimal place except where they are exact, in which cases these exact equivalents are so designated. The equivalents of the imprecise units "tablespoon" and "teaspoon" are rounded to the nearest milliliter.




_______________________
^{1} By action of the 12th General Conference on Weights and Measures (1964) the liter is a special name for the cubic decimeter. ^{2} This section lists units of measurement that have traditionally been used in the United States. In keeping with the Omnibus Trade and Competitiveness Act of 1988, the ultimate objective is to make the International System of Units the primary measurement system used in the United States. ^{3} Squares and cubes of customary but not of metric units are sometimes expressed by the use of abbreviations rather than symbols. For example, sq ft means square foot, and cu ft means cubic foot. ^{4} When necessary to distinguish the liquid pint or quart from the dry pint or quart, the word "liquid" or the abbreviation"liq" should be used in combination with the name or abbreviation of the liquid unit. ^{5} When necessary to distinguish the dry pint or quart from the liquid pint or quart, the word "dry" should be used in combination with the name or abbreviation of the dry unit. ^{6} When necessary to distinguish the avoirdupois dram from the apothecaries dram, or to distinguish the avoirdupois dram or ounce from the fluid dram or ounce, or to distinguish the avoirdupois ounce or pound from the troy or apothecaries ounce or pound, the word"avoirdupois" or the abbreviation "avdp" should be used in combination with the name or abbreviation of the avoirdupois unit. ^{7} When the terms "hundredweight" and "ton" are used unmodified, they are commonly understood to mean the 100pound hundredweight and the 2000pound ton, respectively; these units may be designated "net" or "short" when necessary to distinguish them from the corresponding units in gross or long measure. ^{ }
^{10} The angstrom is basically defined as 10^{10} meter. ^{11} The term "statute mile" originated with Queen Elizabeth I who changed the definition of the mile from the Roman mile of 5000 feet to the statute mile of 5280 feet. The international mile and the U.S. statute mile differ by about 3 millimeters although both are defined as being equal to 5280 feet. The international mile is based on the international foot (0.3048 meter) whereas the U.S. statute mile is based on the survey foot (1200/3937 meter). ^{12} The international nautical mile of 1 852 meters (6 076.115 49...feet) was adopted effective July 1, 1954, for use in the United States. The value formerly used in the United States was 6 080.20 feet = 1 nautical (geographical or sea) mile. ^{13} The question is often asked as to the length of a side of an acre of ground. An acre is a unit of area containing 43 560 square feet. It is not necessarily square, or even rectangular. But, if it is square, then the length of a side is equal to = 208.710+ feet. ^{14} There are a variety of "barrels" established by law or usage. For example, Federal taxes on fermented liquors are based on a barrel of 31 gallons; many State laws fix the "barrel for liquids" as 311/2 gallons; one State fixes a 36gallon barrel for cistern measurement; Federal law recognizes a 40gallon barrel for "proof spirits"; by custom, 42 gallons comprise a barrel of crude oil or petroleum products for statistical purposes, and this is recognized "for liquids" by four States. ^{15} Frequently recognized as 11/4 bushels, struck measure. ^{16} The equivalent "1 teaspoon = 11/3 fluid drams" has been found by the Bureau to correspond more closely with the actual capacities of "measuring" and silver teaspoons than the equivalent "1 teaspoon = 1 fluid dram", which is given by a number of dictionaries. ^{17} Used in assaying. The assay ton bears the same relation to the milligram that a ton of 2000 pounds avoirdupois bears to the ounce troy; hence the mass in milligrams of precious metal obtained from one assay ton of ore gives directly the number of troy ounces to the net ton. ^{18} The gross or long ton and hundredweight are used commercially in the United States to only a very limited extent, usually in restricted industrial fields. The units are the same as the British "ton" and "hundredweight". ^{19} The gross or long ton and hundredweight are used commercially in the United States to only a very limited extent, usually in restricted industrial fields. The units are the same as the British "ton" and "hundredweight". 
For technical questions concerning the Weights and Measures Division, contact us:
Weights and Measures Division, NIST, 100 Bureau Drive, Stop 2600, Gaithersburg, MD 208992600
Phone: (301) 9754004, Fax: (301) 9260647, Email: owm@nist.gov
Date created: November 11, 2000
Last updated: March 6, 2003
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