American Customary and British Imperial Weights and Measures
Length (International)
*|
Base** (inches) |
Customary/Imperial Unit |
Metric Equivalent (underlined figures are exact) |
|
1/254 000 000 in. |
1 angstrom |
0.000 000 1 mm |
|
1/1 000 in. |
1 mil |
0.025 4 mm |
|
1/72 in. |
1 point |
|
|
1/32 in. |
1/32 inch |
0.793 75 mm |
|
1/16 in. |
1/16 inch |
1.587 5 mm |
|
1/6 in. |
1 pica (12 points) |
4.233 3… mm |
|
1 in. |
1 inch |
2.54 cm |
|
2 & 1/4 in. |
1 nail |
5.715 cm |
|
4 in. |
1 hand |
10.16 cm |
|
9 in. |
1 span |
22.86 cm |
|
12 in. |
1 foot |
|
|
18 in. |
1 cubit (2 spans) |
45.72 cm |
|
36 in. |
1 yard (3 ft.) |
0.914 4 m |
|
72 in. |
1 fathom (2 yd.) or (6 ft.) |
1.828 8 m |
|
198 in. |
1 rod, pole, or perch (5 & 1/2 yd.) or (16 & 1/2 ft.) |
5.029 2 m |
|
792 in. |
1 chain (4 rd.) or (22 yd.) |
20.116 8 m |
|
7 920 in. |
1 furlong (10 ch.) |
201.168 m |
|
63 360 in. |
1 mile*** (8 furlongs) or (80 ch.) or (1 760 yd.) or (5 280 ft.) |
1.609 344 km |
|
72 913 & 193/500 in. (72 913.386… in.) |
1 nautical mile**** (2 025.372… yd) or (6076.116… ft.) |
|
|
190 080 in. |
1 league (3 mi.) |
4.828 032 km |
|
5 889 680 121 600 in. |
1 Astronomical Unit (92 955 810 miles) |
149 597 875.088 6… km |
|
372 214 762 027 086 614 & 173 /1 000 in. (372 214 762 027 086 614.173… in.) |
1 light-year (63 197.789… AU) or (5 874 601 673 407.301… mi.) |
9 454 254 955 488 km (exact based on a year of exactly 365 days of 24 hours) |
|
1 217 142 271 828 573 228 & 346 /1 000 in. (1 217 142 271 828 573 228.346… in.) |
1 parsec (3.27 LY) or (206 656.770…AU) or (19 209 947 472 041.875… mi.) |
30 915 413 704 445.76 km |
* The basic unit of English length is the yard, which was originally taken as the distance between the nose of King Henry I's (1068-1135) and the tip of his outstretched arm. In 1866 the official definition of U.S. Customary lengths was set in terms of the meter, 1 inch = 100/3 937 meter, 1 foot = 1 200/3 937 meter, and 1 yard = 3 600/3 937 meter respectively. While these standards continue to be in use for U.S. Survey Measure, in 1959, the Federal government accepted the international standard as the ordinary standard. Thus, now, 1 inch = 127/5 000 meter, 1 foot = 1 524/5 000 meter, and 1 yard = 4 572/5 000 meter respectively. The meter in turn is defined precisely as the length traveled by light in a vacuum during 1/299 792 458 of a second.
**Please be aware that I use the term ‘base’ loosely. I describe all lengths in inches for my own convenience.
***In the United States, the mile does not equal 5 280 feet. The United States statute mile is actually the old United States survey mile. So, in the U.S. be aware that the mile is actually one mile and about three millimeters. There is not enough difference to cause a problem except in land surveying, so priority was given to the needs of land surveyors when we adopted the international standards in 1959.
****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. A speed of 1 nautical mile per hour is 1 knot.
United States Survey Length*
|
Base** (chains) |
Survey Unit |
International Equivalent (underlined figures are exact) |
Metric Equivalent (underlined figures are exact) |
|
1/792 ch. |
|
500 000 /499 999 in.
|
100 /3 937 m (0.025 4… m) |
|
1/100 ch. |
|
(7.92… in.) or (0.66… ft.)
|
792 /3 937 m (0.201 2… m) |
|
1/66 ch. |
|
|
1 200 /3 937 m (0.304 8… m) |
|
1/22 ch. |
|
(1.000 002… yd.) |
|
|
1/4 ch. |
|
(1.000 002… rd.) |
19 800 /3 937 m (5.029 21… m) |
|
1 ch. |
|
(1.000 002… ch.) |
79 200 /3 937 m (20.116 84… m) |
|
10 ch. |
|
(1.000 002… fur.) |
792 000 /3 937 m (201.168 4… m) |
|
80 ch. |
|
|
(1.609 347… km) |
*My source is NIST Document- General Tables of Units of Measurement; available at: http://ts.nist.gov/ts/htdocs/230/235/h4402/appenc.pdf
**Please be aware that I use the term ‘base’ loosely. I describe all lengths in chains for my own convenience.
Area (International)
*|
Base** (square inches) |
Customary/Imperial Unit |
Metric Equivalent*** (underlined figures are exact) |
|
1 sq. in. |
1 square inch |
6.451 6 cm2 |
|
144 sq. in. |
1 square foot |
929.030 4 cm2 |
|
1 296 sq. in. |
1 square yard (9 sq. ft.) |
|
|
39 204 sq. in. |
1 square rod (30 & 1/4) |
25.292 852 64 centiares |
|
627 264 sq. in. |
1 square chain (16 sq. rd.) (484 sq. yd.) |
4.046 856 422 4 ares |
|
1 568 160 sq. in. |
1 rood**** (1 fur. x 1 rd.) (2 & 1/2 sq. ch.) (40 sq. rd.) |
10.117 141 056 ares |
|
6 272 640 sq. in. |
1 acre (1 fur. x 1 ch.)(4 roods)(10 sq. ch.) |
40.468 564 224 ares |
|
4 014 489 600 sq. in. |
1 square mile (640 acres) |
2.589 988 110 336 km2 (258.998 811 033 6 hectares) |
*In the United States, beware. A foot doesn’t always equal a foot. I presume the British use the international standard for area as well as linear measure, but I do not know this for a fact. In America, the foot used to be defined as being exactly 1200/3937 meter or about 30.480 060 96 centimeters. This was the official U.S. definition of the foot from 1866 to 1959; it makes the meter equal exactly 39.37 inches. In 1959 the survey foot was replaced by the international foot, equal to exactly 30.48 centimeters. However, the survey foot remains the basis for precise geodetic surveying in the U.S. The net result is that the survey foot, yard, rod, mile, etc. vary from their international equivalents by a few millimeters. This not a huge difference and thus only presents a problem when very precise measurements are required.
**Please be aware that I use the term ‘base’ loosely. I describe all areas in square inches for my own convenience.
*** These are all exact, but only for international measure.
****The rood is no longer in common usage.
United States Survey Area*
|
Base** (square feet) |
Survey Unit |
International Equivalent (underlined figures are exact) |
Metric Equivalent (underlined figures are exact) |
|
1 sq. ft. |
1 square foot |
250 000 000 000 /249 999 000 001 sq. ft. (1.000 004… sq. ft.) |
1 440 000 /15 499 969 m2 (0.092 9… m2) |
|
272 & 1/4 sq. ft. |
1 square rod |
250 000 000 000 /249 999 000 001 sq. rd. (1.000 004… sq. rd.) |
(25.293 0… centiares) |
|
4 356 sq. ft. |
1 square chain (16 sq. rd.) |
250 000 000 000 /249 999 000 001 sq. ch. (1.000 004… sq. ch.) |
6 272 640 000 /15 499 969 m2
|
|
43 560 sq. ft. |
1 acre (1 fur. x 1 ch.)(4 roods)(10 sq. ch.) |
250 000 000 000 /249 999 000 001 acres (1.000 004… acres) |
62 726 400 000 /15 499 969 m2
|
|
27 878 400 sq. ft. |
1 square mile (640 acres) |
250 000 000 000 /249 999 000 001 sq. mi. (1.000 004… sq. mi.) |
40 144 896 000 000 /15 499 969 m2
|
*My source is NIST Document- General Tables of Units of Measurement; available at: http://ts.nist.gov/ts/htdocs/230/235/h4402/appenc.pdf
**Please be aware that I use the term ‘base’ loosely. I describe all areas in square feet for my own convenience.
Volume
|
Base* (cubic inches) |
Customary/Imperial Unit |
Metric Equivalent (underlined figures are exact) |
|
1 cu. in. |
1 cubic inch |
16.387 064 cm3 |
|
1 728 cu. in. |
1 cubic foot |
28 316.846 592 cm3 |
|
46 656 cu. in. |
1 cubic yard (9 sq. ft.) |
764 554.857 984 cm3 |
*Please be aware that I use the term ‘base’ loosely. I describe all volumes in cubic inches for my own convenience.
British Imperial Liquid/Dry Capacity
|
Base* (fluid ounces) |
Imperial Unit |
Metric Equivalent (underlined figures are exact) |
|
1/480 fl. oz. |
1 minim** |
0.059 194… mL |
|
1/160 fl. oz. |
1 fluid scruple** (3 min. |
|
|
1/8 fl. oz. |
|
3.551 632 812 5 mL |
|
1 fl. oz. |
1 fluid ounce*** (8 fl. dr.) |
|
|
5 fl. oz. |
1 gill |
142.065 312 5 mL |
|
20 fl. oz. |
1 pint (4 gi.) |
568.261 25 mL |
|
40 fl. oz. |
1 quart (2 pt.) |
1.136 522 5 L |
|
160 fl. oz. |
1 gallon (4 qt)(10 lbs. exactly)( 4 535.923 7g exactly) |
4.546 09 L |
|
320 fl. oz. |
1 peck (2 gal.) |
9.092 18 L |
|
1 280 fl. oz. |
1 bushel (4 pk.) or (8 gal.) |
36.368 72 L |
|
35 840 fl. oz. |
1 water ton (28 bu.) or (224 gal.) |
|
|
46 080 fl. oz. |
1 chaldron (36 bu.) or (288 gal.) |
1 309.273 92 L |
*Please be aware that I use the term ‘base’ loosely. I describe all capacity measures in fluid ounces for my own convenience.
**These capacity measures are usually considered to be specifically for use in medicine (Apothecaries’ fluid measure).
***1 imperial fluid ounce is equal to approximately 1 & 117 421/160 000 (1.733 874 963) cubic inches. 1 imperial fluid ounce of water is equal to 1 avdp. ounce. It is smaller than the customary fluid ounce.
British Imperial Kitchen Measure
|
Base* (gills) |
Imperial Unit |
Metric Equivalent (underlined figures are exact) |
|
1/1 824 gi. |
1 drop (1/76 tsp)** |
0.077 9… mL |
|
1/1 440 gi. |
1 drop (1/60 tsp.)** |
0.098 7… mL |
|
1/384 gi. |
1 dash (4 & 3/4 drops) or (3 & 3/4 drops) |
0.369 962 5 mL |
|
1/192 gi. |
1 pinch (2 dashes) |
0.739 924… mL |
|
1/24 gi. |
1 teaspoon (8 pinches) |
5.919 4… mL |
|
1/12 gi. |
1 dessertspoon (2 tsp.) |
11.838 8… mL |
|
1/8 gi. |
1 tablespoon (3 tsp.) |
17.758 164 062 5 mL |
|
1/5 gi. |
1 fluid ounce (1 & 3/5 tbsp.) |
28.413 062 5 mL |
|
1 gi. |
1 gill (8 tbsp.) |
142.065 312 5 mL |
|
2 gi. |
1 breakfast cup |
284.130 625 mL |
|
4 gi. |
1 pint |
568.261 25 mL |
|
8 gi. |
1 quart |
1.136 522 5 L |
|
32 gi. |
1 gallon |
|
* Please be aware that I use the term ‘base’ loosely. I describe all kitchen capacity measures in gills for my own convenience.
**I have seen both of these values given for the drop.
American Customary Liquid Capacity
|
Base* (fluid ounces) |
Customary Unit |
Metric Equivalent (underlined figures are exact) |
|
1/480 fl. oz. |
1 minim** |
0.061 611 519 92 187 5 mL |
|
1/8 fl. oz. |
|
3.696 691 195 312 5 mL |
|
1 fl. oz. |
1 fluid ounce*** (8 fl. dr.) |
29.573 529 562 5 mL |
|
4 fl. oz. |
1 gill |
118.294 118 25 mL |
|
8 fl. oz. |
1 cup (2 gi.) |
236.588 236 5 mL |
|
16 fl. oz. |
1 pint (2 cups or 4 gi.) |
473.176 473 mL |
|
32 fl. oz. |
1 quart (2 pt.) |
|
|
128 fl. oz. |
1 gallon (4 qt.) |
3.785 411 784 L |
*Please be aware that I use the term ‘base’ loosely. I describe all liquid capacity measures in fluid ounces for my own convenience.
**These capacity measures are usually considered to be specifically for use in medicine.
***1 customary fluid ounce is equal to exactly 1 & 103/128 (1.804 687 5) cubic inches. It is larger than an imperial fluid ounce and its weight in water is about 1 & 1/24 avdp. ounces.
American Customary Dry Capacity
|
Base* (dry pints) |
Customary Unit |
Metric Equivalent (underlined figures are exact) |
|
1 dry pt. |
1 dry pint** |
550.610 471 357 5 mL |
|
2 dry pt. |
1 dry quart |
1.101 220 942 715 L |
|
16 dry pt. |
1 peck |
|
|
64 dry pt. |
1 bushel (2 150.42 cu. in. exactly)*** |
|
*Please be aware that I use the term ‘base’ loosely. I describe all dry capacity measures in pints for my own convenience.
**1 dry pint equals exactly 33.600 312 5 cubic inches; it is somewhat larger than the customary liquid pint which is only 28.875 cu. in.
***Exact according to NIST Document- General Tables of Units of Measurement; available at: http://ts.nist.gov/ts/htdocs/230/235/h4402/appenc.pdf
American Customary Kitchen Measure
|
Base* (fluid ounces) |
Customary Unit |
Metric Equivalent (underlined figures are exact) |
|
1/456 fl. oz. |
1 drop (1/76 tsp)** |
0.064 9… mL |
|
1/360 fl. oz. |
1 drop (1/60 tsp.)* * |
0.082 1… mL |
|
1/96 fl. oz. |
1 dash (4 & 3/4 drops) or (3 & 3/4 drops) |
0.308 057 599 609 375 mL |
|
1/48 fl. oz. |
1 pinch (2 dashes) |
0.616 115 199 218 75 mL |
|
1/6 fl. oz. |
1 teaspoon (8 pinches) |
4.928 921 593 75 mL |
|
1/2 fl. oz. |
1 tablespoon (3 tsp.) |
14.786 764 781 25 mL |
|
1 fl. oz. |
1 fluid ounce (2 tbsp.) |
29.573 529 562 5 mL |
|
8 fl. oz. |
1 cup |
236.588 236 5 mL |
|
16 fl. oz. |
1 pint |
473.176 473 mL |
|
32 fl. oz. |
1 quart |
|
|
128 fl. oz. |
1 gallon |
3.785 411 784 L |
* Please be aware that I use the term ‘base’ loosely. I describe all kitchen capacity measures in fluid ounces for my own convenience.
**I have seen both of these values given for the drop.
Approximate Conversion Factors for Customary and Imperial Capacity
Avoirdupois Mass (Colloquial Weight)
|
Base* (ounces) |
Customary/Imperial Unit |
Metric Equivalent (underlined figures are exact) |
|
1/32 grain |
2.024 965 937 5 mg |
|
2/875 oz. |
1 grain |
|
|
1/16 oz. |
1 dram (27 & 11/32 gr.) |
1.771 845 195 312 5 g |
|
1 oz. |
1 ounce** (16 dr.) or (437 & 1/2 gr.) |
|
|
16 oz. |
1 pound (7 000 gr.) |
453.592 37*** g |
|
112 oz. |
1 clove (7 lbs.) |
3.175 146 59 kg |
|
224 oz. |
1 stone (14 lbs.) |
6.350 293 18 kg |
|
400 oz. |
1 quarter (short, Customary)(25 lbs.) |
|
|
448 oz. |
1 long quarter (Imperial)(2 stone) |
|
|
1 600 oz. |
1 hundredweight (short, Customary)(100 lbs.) |
|
|
1 792 oz. |
1 long hundredweight (Imperial)(112 lbs.) |
|
|
32 000 oz. |
1 ton (short, Customary)(2 000 lbs.) |
907.184 74 kg |
|
35 840 oz. |
1 long ton (Imperial)(2 240 lbs.) |
1.016 046 908 8 t |
*Please be aware that I use the term ‘base’ loosely. I describe all mass measures in ounces for my own convenience.
**1 ounce is the mass of approximately 1 & 117 421/160 000 (1.733 874 963) cubic inches of distilled water at maximum density.
***Exact according to NIST Document- General Tables of Units of Measurement; available at: http://ts.nist.gov/ts/htdocs/230/235/h4402/appenc.pdf
Troy Mass
* (Colloquial Weight)|
Base** (grains) |
Customary/Imperial Unit |
Metric Equivalent |
|
1 gr. |
1 grain (equals 1 gr. avdp., also1 gr. ap.) |
64.798 91 mg |
|
3 & 54/625*** gr. (3.086… gr.) |
1 carat**** |
200 mg |
|
24 gr. |
1 pennyweight |
|
|
480 gr. |
1 ounce***** (20 dwt.) |
31.103 476 8 g |
|
5 760 gr. |
|
373.241 721 6 g |
* Used in weighing gold, silver, and precious stones
** Please be aware that I use the term ‘base’ loosely. I describe all troy measures in grains for my own convenience.
*** Not exact.
**** The carat is mainly used in measuring diamonds, its mass has been fixed at exactly 200 mg according to NIST Document- General Tables of Units of Measurement; available at: http://ts.nist.gov/ts/htdocs/230/235/h4402/appenc.pdf
***** 1 troy ounce is the mass of approximately 1 & 451/500 (1.902 308 530) cubic inches of distilled water at maximum density and is equal to 1 apothecaries’ ounce.
Apothecaries’ Mass
* (Colloquial Weight)|
Base* (grains) |
Customary/Imperial Unit |
Metric Equivalent |
|
1 gr. |
1 grain (equals 1 gr. avdp., also 1 gr.t.) |
64.798 91 mg |
|
20 gr. |
1 scruple |
1.295 978 2 g |
|
60 gr. |
1 dram (3 s. ap.) |
3.887 934 6 g |
|
480 gr. |
1 ounce*** (8 dr. ap.) |
31.103 476 8 g |
|
5 760 gr. |
1 apothecaries’ pound (12 oz. ap.) |
|
* Used in weighing medicines
** Please be aware that I use the term ‘base’ loosely. I describe all apothecaries’ measures in grains for my own convenience.
***1 apothecaries’ ounce is the mass of approximately 1 & 451/500 (1.902 308 530) cubic inches of distilled water at maximum density and is equal to 1 troy ounce.
Abbreviations -
-Linear Units
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-Area Units
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-Volume Units
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-Capacity Units
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-Mass Units
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