Conversion of units refers to conversion factors between units of measurement.
Techniques
The simplest way to convert from one unit to another is to carry through the units themselves in the mathematical operation. To illustrate this process, consider the following examples.
You would like to convert 6 feet into metres. Consulting the table below and finding that one foot is exactly 0.3048 metre, you can now perform the mathematical conversion:
- 6 ft × 0.3048 m/ft = 1.8288 m
Notice that the "foot" units canceled out, leaving only metres, the desired result. (Since 0.3048 metre per foot have infinite precision, the precision of the answer is determined by the precision of the 6 ft figure; if, for example, you are defining the fathom, expressing it with 5 significant figures is correct. But if the 6 ft figure is a measurement, the result needs to be rounded appropriately.)
Say your height is 183 centimetres, and you wish to convert this into inches:
- 183 cm / (2.54 cm/in) = 72.0 in
To check our answer, we convert this result back into feet:
- 72 in / (12 in/ft) = 6.0 feet
which confirms the earlier result.
Multiple units can be manipulated in the same fashion:
- 7 mi/s × 1.609344 km/mi × 3600 s/h = 40,000 km/h
Thus, Earth escape velocity is about 7 miles per second, or 40,000 kilometres per hour. Notice that since the calculation started with one significant figure (the 7), the answer also has one significant figure (the 4 in 40,000).
Deciding whether to multiply or divide is determined by looking at the units and deciding which ones you want to "get rid" of. In the conversion just above, if we had divided by 3600 s/h instead of multiplying, the result would have come out in kilometre-hours per square second, clearly an incorrect and meaningless result.
Rounding of results
An important thing to remember is that the process of making a conversion cannot give you any more precise results than what you started with. While many of the conversion factors given in the tables below are exact, and others while not exact contain many significant digits, not all the numbers you get after performing calculations on a calculator or with pencil and paper are meaningful.
After using these conversion factors, be sure to round off the results appropriately.
Tables of conversion factors
Legend
Legend
| ≡
|
definition
|
| =
|
exactly equal to
|
| ≈
|
approximately equal to
|
| (digits)
|
indicates the digits repeat infinitely
|
Length
Length, l
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
| angstrom |
Å
|
|
≡ 1.000 x 10-10 m = 0.1 nm
|
| astronomical unit |
AU
|
|
= 149 597 870.691 ± 0.030 km
|
| atomic unit of length |
au
|
≡ a0
|
≈ 5.291 772 083 x 10-11 ± 19 x 10-20 m
|
| barley corn |
|
≡ 1/3 in
|
≈ 8.466 667 mm
|
| Bohr radius |
a0; b
|
≡ α/(4πR∞)
|
≈ 5.291 772 083Template:E ± 19 x 10-20 m
|
| cable length (Imperial) |
|
≡ 608 ft
|
= 185.3184 m
|
| cable length (International) |
|
≡ 1/10 NM
|
= 185.2 m
|
| cable length (U.S.) |
|
≡ 720 ft
|
= 219.456 m
|
| calibre |
cal
|
≡ 1 in
|
= 25.4 mm
|
| chain (Gunter's; Surveyor's) |
ch
|
≡ 66 ft
|
= 20.1168 m
|
| chain (Ramsden's Engineer's) |
ch
|
≡ 100 ft
|
= 30.48 m
|
| cubit |
|
≡ 18 in
|
= 0.4572 m
|
| ell |
ell
|
≡ 45 in
|
= 1.143 m
|
| fathom |
fm
|
≡ 6 ft
|
= 1.8288 m
|
| ≈ 1/1000 NM
|
= 1.852 m
|
| fermi |
fm
|
≡ 1.000 x 10-15 m
|
= 1.000 x 10-15 m
|
| finger |
|
≡ 7/8 in
|
= 22.225 mm
|
| finger (cloth) |
|
≡ 4 ½ in
|
= 0.1143 m
|
| foot (Benoît) |
ft (Ben)
|
|
≈ 0.304 799 735 m
|
| foot (Clarke's; Cape) |
ft (Cla)
|
|
≈ 0.304 797 265 4 m
|
| foot (Indian) |
ft Ind
|
|
≈ 0.304 799 514 m
|
| foot (International) |
ft
|
≡ 1/3 yard
|
= 0.3048 m
|
| foot (Sear's) |
ft (Sear)
|
|
≈ 0.304 799 47 m
|
| foot (U.S. Survey) |
ft (US)
|
≡ 1200/3937 m [1]
|
≈ 0.304 800 610 m
|
| furlong |
fur
|
≡ 660 ft
|
= 201.168 m
|
| geographical mile |
mi
|
≡ 6082 ft
|
= 1853.7936 m
|
| hand |
|
≡ 4 in
|
= 0.1016 m
|
| inch |
in
|
≡ 1/36 yd
|
= 25.4 mm
|
| league |
lea
|
≡ 3 mi
|
= 4828.032 m
|
| light-day |
|
≡ 24 light-hours
|
= 2.590 206 837 12Template:E m
|
| light-hour |
|
≡ 60 light-minutes
|
= 1.079 252 848 8Template:E m
|
| light-minute |
|
≡ 60 light-seconds
|
= 1.798 754 748Template:E m
|
| light-second |
|
|
≡ 2.997 924 58Template:E m
|
| light-year |
l.y.
|
≡ c0 × 86 400 × 365.25
|
= 9.460 730 472 580 8Template:E m
|
| line |
ln
|
≡ 1/12 in (Klein 1988, 63)
|
≈ 2.116 667 mm
|
| link (Gunter's; Surveyor's) |
lnk
|
≡ 1/100 ch
|
= 0.201 168 m
|
| link (Ramsden's; Engineer's) |
lnk
|
≡ 1 ft
|
= 0.3048 m
|
| metre (SI base unit) |
m
|
≡ 1 m
|
= 1 m
|
| mickey |
|
≡ 1/200 in
|
= 1.27 x 10-4 m
|
| micron |
µ
|
|
≡ 1.000 x 10-6 m
|
| mil; thou |
mil
|
≡ 1.000 x 10-3 in
|
= 2.54 x 10-5 m
|
| mile |
mi
|
≡ 1760 yd = 5280 ft
|
= 1609.344 m
|
| mile (U.S. Survey) |
mi
|
≡ 5280 ft (US)
|
= 5280 × 1200/3937 m ≈ 1609.347 219 m
|
| nail (cloth) |
|
≡ 2 ¼ in
|
= 57.15 mm
|
| nautical league |
NL; nl
|
≡ 3 NM
|
= 5556 m
|
| nautical mile |
NM; nm
|
|
≡ 1852 m
|
| nautical mile (Admiralty) |
NM (Adm); nm (Adm)
|
≡ 6080 ft
|
= 1853.184 m
|
| pace |
|
≡ 2.5 ft
|
= 0.762 m
|
| palm |
|
≡ 3 in
|
= 76.2 mm
|
| parsec |
pc
|
≈ 180 × 60 × 60/π AU
≈ 206 264.806 25 AU
= 3.261 563 776 9 ± 6 Template:E light-years
|
= 3.085 677 581 3Template:E ± 6Template:E m
|
| point (ATA) |
pt
|
≡ 0.013837 in
|
= 0.351 459 8 mm
|
| point (Didot; European) |
pt
|
|
≡ 0.376 065 mm
|
| point (metric) |
pt
|
≡ 3/8 mm
|
= 0.375 mm
|
| point (PostScript) |
pt
|
≡ 1/72 in
|
≈ 0.352 778 mm
|
| quarter |
|
≡ ¼ yd
|
= 0.2286 m
|
| rod; pole; perch |
rd
|
≡ 16 ½ ft
|
= 5.0292 m
|
| rope |
rope
|
≡ 20 ft
|
= 6.096 m
|
| span |
|
≡ 6 in
|
= 0.1524 m
|
| span (cloth) |
|
≡ 9 in
|
= 0.2286 m
|
| spatTemplate:Citation needed |
S
|
≡ 1012 m
|
= 1 Tm
|
| stick |
|
≡ 2 in
|
= 50.8 mm
|
| stigma; pm |
|
≡ 1.000 x 10-12 m
|
≡ 1.000 x 10-12 m
|
| telegraph mile |
mi
|
≡ 6087 ft
|
= 1855.3176 m
|
| twip |
twp
|
≡ 1/1440 in
|
≈ 1.763 889Template:E m
|
| x unit; siegbahn |
xu
|
|
≈ 1.0021 x 10-13 m
|
| yard (International) |
yd
|
≡3 ft ≡ 0.9144 m [1]
|
= 0.9144 m
|
Area
Area, A
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
| acre |
ac
|
≡ 10 sq ch = 4840 sq yd
|
= 4046.856 422 4 m²
|
| are |
a
|
|
≡ 100 m²
|
| barn |
b
|
|
≡ 10−28 m²
|
| barony |
|
≡ 4000 ac
|
= 1.618 742 568 96 x 107 m²
|
| board |
bd
|
≡ 1 in × 1 ft
|
= 7.741 92 x 10-3 m²
|
| boiler horsepower equivalent direct radiation |
bhp EDR
|
≡ (1 ft²) (1 bhp) / (240 BTUIT/h)
|
≈ 12.958 174 m²
|
| circular inch |
circ in
|
≡ π/4 in²
|
≈ 5.067 075 x 10-4 m²
|
| circular mil; circular thou |
circ mil
|
≡ π/4 mil²
|
≈ 5.067 075 x 10-10 m²
|
| cord |
|
≡ 192 bd
|
= 1.486 448 64 m²
|
| dunam |
|
≡ 1000 m²
|
= 1000 m²
|
| hectare |
ha
|
≡ 10 000 m²
|
= 0.01 km²
|
| hide |
|
≡ 100 ac
|
= 4.046 856 422 4 x 105 m²
|
| rood |
ro
|
≡ ¼ ac
|
= 1011.714 105 6 m²
|
| square chain |
sq ch
|
≡ 1 ch²
|
= 404.685 642 24 m²
|
| square foot |
sq ft
|
≡ 1 ft²
|
= 9.290 304 x 10-2 m²
|
| square inch |
sq in
|
≡ 1 in²
|
= 6.4516Template:E m²
|
| square kilometre |
km²
|
≡ 1 km²
|
= 106 m²
|
| square link |
sq lnk
|
≡ 1 lnk²
|
= 4.046 856 422 4 x 10-2 m²
|
| square metre (SI unit) |
m²
|
≡ 1 m × 1 m
|
= 1 m²
|
| square mil; square thou |
sq mil
|
≡ 1 mil²
|
= 6.4516 x 10-10 m²
|
| square mile; section |
sq mi
|
≡ 1 mi²
|
= 2.589 988 110 336 x 106 m²
|
| square rod/pole/perch |
sq rd
|
≡ 1 rd²
|
= 25.292 852 64 m²
|
| square U.S. Survey mile |
sq mi
|
≡ 1 mi (US)²
|
≈ 2.589 998 x 106 m²
|
| square yard |
sq yd
|
≡ 1 yd²
|
= 0.836 127 36 m²
|
| township |
|
≡ 36 sq mi (US)
|
≈ 9.323 994Template:E m²
|
| yardland |
|
≡ 30 ac
|
= 1.214 056 926 72 x 105 m²
|
Volume
Volume, V
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
| cubic metre (SI unit) |
m³
|
≡ 1 m × 1 m × 1 m
|
|
| litre |
L
|
|
≡ 1 dm³
|
| lambda |
λ
|
≡ 1 mm³
|
= 1 μL
|
| drop (metric) |
|
≡ 1/20 mL
|
= 0.05 mL
|
| minim (Imperial) |
min
|
≡ 1/480 fl oz (Imp) = 1/60 fl dr (Imp)
|
≈ 0.059 193 880 208 333 mL
|
| minim (U.S.) |
min
|
≡ 1/480 US fl oz = 1/60 US fl dr
|
= 0.061 611 519 921 875 mL
|
| drop (U.S.) (alt) |
gtt
|
≡ 1/456 US fl oz
|
≈ 0.064 854 231 mL
|
| drop (Imperial) (alt) |
gtt
|
≡ 1/1824 gi (Imp)
|
≈ 0.077 886 684 mL
|
| drop (U.S.) |
gtt
|
≡ 1/360 US fl oz
|
= 0.082 148 693 229 1(6) mL
|
| drop (medical) |
|
≡ 1/12 mL
|
= 0.08(3) mL
|
| drop (Imperial) |
gtt
|
≡ 1/288 fl oz (Imp)
|
= 0.098 656 467 013 (8) mL
|
| dash (U.S.) |
|
≡ 1/96 US fl oz = ½ US pinch
|
= 0.308 057 599 609 375 mL
|
| dash (Imperial) |
|
≡ 1/384 gi (Imp) = ½ pinch (Imp)
|
= 0.369 961 751 302 08(3) mL
|
| pinch (U.S.) |
|
≡ 1/48 US fl oz = 1/8 US tsp |
= 0.616 115 199 218 75 mL
|
| pinch (Imperial) |
|
≡ 1/192 gi (Imp) = 1/8 tsp (Imp)
|
= 0.739 923 502 604 1(6) mL
|
| fluid scruple (Imperial) |
fl s
|
≡ 1/24 fl oz (Imp)
|
= 1.183 877 604 1(6) mL
|
| fluid drachm (Imperial) |
fl dr
|
≡ 1/8 fl oz (Imp)
|
= 3.551 632 812 5 mL
|
| fluid dram (U.S.); U.S. fluidram |
fl dr
|
≡ 1/8 US fl oz
|
= 3.696 691 195 312 5 mL
|
| teaspoon (Canadian) |
tsp
|
≡ 1/6 fl oz (Imp)
|
≈ 4.735 510 416 667 mL
|
| teaspoon (U.S.) |
tsp
|
≡ 1/6 US fl oz
|
= 4.928 921 595 mL
|
| teaspoon (metric) |
|
|
≡ 5 mL
|
| teaspoon (Imperial) |
tsp
|
≡ 1/24 gi (Imp)
|
= 5.919 388 020 8(3) mL
|
| dessertspoon (Imperial) |
|
≡ 1/12 gi (Imp)
|
= 11.838 776 041 (6) mL
|
| tablespoon (Canadian) |
tbsp
|
≡ ½ fl oz (Imp)
|
= 14.206 531 25 mL
|
| tablespoon (U.S.) |
tbsp
|
≡ ½ US fl oz
|
= 14.786 764 782 5 mL
|
| tablespoon (metric) |
|
|
≡ 15 mL
|
| cubic inch |
cu in
|
≡ 1 in³
|
= 16.387 064 mL
|
| tablespoon (Imperial) |
tbsp
|
≡ 5/8 fl oz (Imp)
|
= 17.758 164 062 5 mL
|
| pony |
|
≡ 3/4 US fl oz
|
= 22.180 147 171 875 mL
|
| fluid ounce (Imperial) |
fl oz (Imp)
|
≡ 1/160 gal (Imp)
|
= 28.413 062 5 mL
|
| fluid ounce (U.S.) |
fl oz (US)
|
≡ 1/128 gal (US)
|
= 29.573 529 562 5 mL
|
| shot |
|
≡ 1 US fl oz
|
= 29.573 529 562 5 mL
|
| jigger |
|
≡ 1 ½ US fl oz
|
= 44.360 294 343 75 mL
|
| gill (U.S.) |
gi (US)
|
≡ 4 US fl oz
|
= 118.294 118 25 mL
|
| gill (Imperial); Noggin |
gi (Imp); nog
|
≡ 5 fl oz (Imp)
|
= 142.065 312 5 mL
|
| cup (Canadian) |
c (CA)
|
≡ 8 fl oz (Imp)
|
= 227.3045 mL
|
| cup (U.S.) |
c (US)
|
≡8 US fl oz ≡ 1/16 gal (US)
|
= 236.588 236 5 mL
|
| cup (metric) |
c
|
|
≡ 250 mL
|
| breakfast cup |
|
≡ 10 fl oz (Imp)
|
= 284.130 625 mL
|
| pint (U.S. fluid) |
pt (US fl)
|
≡ 1/8 gal (US)
|
= 473.176 473 mL
|
| pint (U.S. dry) |
pt (US dry)
|
≡ 1/4 bu (US lvl)
|
= 0.550 610 471 357 5 L
|
| pint (Imperial) |
pt (Imp)
|
≡ 1/8 gal (Imp)
|
= 0.568 261 25 L
|
| fifth |
|
≡ 1/5 US gal
|
= 0.757 082 356 8 L
|
| quart (U.S. fluid) |
qt (US)
|
≡ 1/4 gal (US fl)
|
= 0.946 352 946 L
|
| quart (U.S. dry) |
qt (US)
|
≡ 1/32 bu (US lvl) = ¼ gal (US dry)
|
= 1.101 220 942 715 L
|
| quart (Imperial) |
qt (Imp)
|
≡ ¼ gal (Imp)
|
= 1.136 522 5 L
|
| pottle; quartern |
|
≡ ½ gal (Imp) = 80 fl oz (Imp)
|
= 2.273 045 L
|
| board-foot |
fbm
|
≡ 144 cu in
|
= 2.359 737 216 L
|
| gallon (U.S. fluid; Wine) |
gal (US)
|
≡ 231 cu in
|
= 3.785 411 784 L
|
| gallon (U.S. dry) |
gal (US)
|
≡ 1/8 bu (US lvl)
|
= 4.404 883 770 86 L
|
| gallon (Imperial) |
gal (Imp)
|
≡
|
= 4.546 09 L
|
| beer gallon |
beer gal
|
≡ 282 cu in
|
= 4.621 152 048 L
|
| peck (U.S. dry) |
pk
|
≡ ¼ US lvl bu
|
= 8.809 767 541 72 L
|
| peck (Imperial) |
pk
|
≡ 2 gal (Imp)
|
= 9.092 18 L
|
| bucket (Imperial) |
bkt
|
≡ 4 gal (Imp)
|
= 18.184 36 L
|
| timber foot |
|
≡ 1 cu ft
|
= 28.316 846 592 L
|
| cubic foot |
cu ft
|
≡ 1 ft × 1 ft × 1 ft
|
= 28.316 846 592 L
|
| firkin |
|
≡ 9 gal (US)
|
= 34.068 706 056 L
|
| bushel (U.S. dry level) |
bu (US lvl)
|
≡ 2150.42 cu in
|
= 35.239 070 166 88 L
|
| bushel (Imperial) |
bu (Imp)
|
≡ 8 gal (Imp)
|
= 36.368 72 L
|
| bushel (U.S. dry heaped) |
bu (US)
|
≡ 1 ¼ bu (US lvl)
|
= 44.048 837 708 6 L
|
| strike (U.S.) |
|
≡ 2 bu (US lvl)
|
= 70.478 140 333 76 L
|
| strike (Imperial) |
|
≡ 2 bu (Imp)
|
= 72.737 44 L
|
| kilderkin |
|
≡ 18 gal (Imp)
|
= 81.829 62 L
|
| sack (U.S.) |
|
≡ 3 bu (US lvl)
|
= 105.717 210 500 64 L
|
| sack (Imperial); bag |
|
≡ 3 bu (Imp)
|
= 109.106 16 L
|
| barrel (U.S. dry) |
bl (US)
|
≡ 105 qt (US) = 105/32 bu (US lvl)
|
= 115.628 198 985 075 L
|
| barrel (U.S. fluid) |
fl bl (US)
|
≡ 31 ½ gal (US)
|
= 119.240 471 196 L
|
| coomb |
|
≡ 4 bu (Imp)
|
= 145.474 88 L
|
| barrel (petroleum) |
bl
|
≡ 42 gal (US)
|
= 158.987 294 928 L
|
| barrel (Imperial) |
bl (Imp)
|
≡ 36 gal (Imp)
|
= 163.659 24 L
|
| hogshead (U.S.) |
hhd (US)
|
≡ 2 fl bl (US)
|
= 238.480 942 392 L
|
| seam |
|
≡ 8 bu (US lvl)
|
= 281.912 561 335 04 L
|
| quarter; pail |
|
≡ 8 bu (Imp)
|
= 290.949 76 L
|
| hogshead (Imperial) |
hhd (Imp)
|
≡ 2 bl (Imp)
|
= 327.318 48 L
|
| cord-foot |
|
≡ 16 cu ft
|
= 0.453 069 545 472 m³
|
| butt, pipe |
|
≡ 126 gal (wine)
|
= 0.476 961 884 784 m³
|
| perch |
per
|
≡ 16 ½ ft × 1 1/2 ft × 1 ft
|
= 0.700 841 953 152 m³
|
| cubic yard |
cu yd
|
≡ 27 cu ft
|
= 0.764 554 857 984 m³
|
| tun |
|
≡ 252 gal (wine)
|
= 0.953 923 769 568 m³
|
| displacement ton |
|
≡ 35 cu ft
|
= 0.991 089 630 72 m³
|
| water ton |
|
≡ 28 bu (Imp)
|
= 1.018 324 16 m³
|
| freight ton |
|
≡ 40 cu ft
|
= 1.132 673 863 68 m³
|
| wey (U.S.) |
|
≡ 40 bu (US lvl)
|
= 1.409 562 806 675 2 m³
|
| load |
|
≡ 50 cu ft
|
= 1.415 842 329 6 m³
|
| register ton |
|
≡ 100 cu ft
|
= 2.831 684 659 2 m³
|
| last |
|
≡ 80 bu (Imp)
|
= 2.909 497 6 m³
|
| cord (firewood) |
|
≡ 8 ft × 4 ft × 4 ft
|
= 3.624 556 363 776 m³
|
| cubic fathom |
cu fm
|
≡ 1 fm × 1 fm × 1 fm
|
= 6.116 438 863 872 m³
|
| acre-inch |
|
≡ 1 ac × 1 in
|
= 102.790 153 128 96 m³
|
| acre-foot |
|
≡ 1 ac × 1 ft
|
= 1233.481 837 547 52 m³
|
| cubic mile |
cu mi
|
≡ 1 mi³
|
= 4.168 181 825 440 579 584 km³
|
Angle
Solid angle
Mass
Mass, m
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
Relation to avoirdupois units
|
| kilogram |
kg
|
|
(SI base unit)
|
| electron rest mass |
me
|
|
≈ 9.109 381 88 x 10-31 ± 72 x 10-39 kg
|
| atomic unit of mass |
au
|
≡ me
|
≈ 9.109 381 88 x 10-31 ± 72 x 10-39 kg
|
| unified atomic mass unit |
amu
|
|
≈ 1.660 538 73 x 10-27 ± 13 x 10-35 kg
|
| dalton |
Da
|
|
≈ 1.660 902 10 x 10-27 ± 13 x 10-35 kg
|
| gamma |
γ
|
|
≡ 1 μg
|
| point |
|
≡ 1/100 kt (metric)
|
= 2 mg
|
| mite |
|
≡ 1/20 gr
|
= 3.239 945 5 mg
|
| mite (metric) |
|
≡ 1/20 g
|
= 50 mg
|
| grain |
gr
|
|
≡ 64.798 91 mg
|
| crith |
|
|
≈ 89.9349 mg
|
| carat (metric) |
kt
|
|
≡ 200 mg
|
| carat |
kt
|
≡ 3 1/6 gr
|
≈ 205.196 548 333 mg
|
| sheet |
|
≡ 1/700 lb av
|
= 647.9891 mg
|
| scruple (avoirdupois) |
s av
|
≡ 20 gr
|
= 1.295 978 2 g
|
| pennyweight |
dwt; pwt
|
≡ 1/20 oz t
|
= 1.555 173 84 g
|
| dram (avoirdupois) |
dr av
|
≡ 27 11/32 gr
|
= 1.771 845 195 312 5 g
|
| dram (apothecary; troy) |
dr t
|
≡ 60 gr
|
= 3.887 934 6 g
|
| hyl (CGS unit) |
|
≡ 1 gee × 1 g × 1 s²/m
|
= 9.806 65 g
|
| ounce (avoirdupois) |
oz av
|
≡ 1/16 lb
|
= 28.349 523 125 g
|
| assay ton (short) |
AT
|
≡ 1 mg × 1 sh tn ÷ 1 oz t
|
≈ 29.166 667 g
|
| ounce (apothecary; troy) |
oz t
|
≡ 1/12 lb t
|
= 31.103 476 8 g
|
| assay ton (long) |
AT
|
≡ 1 mg × 1 long tn ÷ 1 oz t
|
≈ 32.666 667 g
|
| mark |
|
≡ 8 oz t
|
= 248.827 814 4 g
|
| pound (troy) |
lb t
|
≡ 5760 grains
|
= 0.373 241 721 6 kg
|
| pound (avoirdupois) |
lb av
|
≡ 7000 grains
|
= 0.453 592 37 kg
|
| pound (metric) |
|
|
≡ 500 g
|
| clove |
|
≡ 8 lb av
|
= 3.628 738 96 kg
|
| stone |
st
|
≡ 14 lb av
|
= 6.350 293 18 kg
|
| hyl (MKS unit) |
|
≡ 1 gee × 1 kg × 1 s²/m
|
= 9.806 65 kg
|
| quarter (Imperial) |
|
≡ 1/4 long cwt = 2 st = 28 lb av
|
= 12.700 586 36 kg
|
| slug; geepound |
slug
|
≡ 1 gee × 1 lb av × 1 s²/ft
|
≈ 14.593 903 kg
|
| bag (Portland cement) |
|
≡ 94 lb av
|
= 42.637 682 78 kg
|
| short hundredweight; cental |
sh cwt
|
≡ 100 lb av
|
= 45.359 237 kg
|
| long hundredweight |
long cwt or cwt
|
≡ 112 lb av
|
= 50.802 345 44 kg
|
| bag (coffee)
|
|
≡ 60 kg
|
= 60 kg
|
| quintal (metric) |
q
|
|
≡ 100 kg
|
| wey |
|
≡ 252 lb = 18 st
|
= 114.305 277 24 kg (variants exist)
|
| long quarter |
|
≡ ¼ long tn
|
= 254.011 727 2 kg
|
| kip |
kip
|
≡ 1000 lb av
|
= 453.592 37 kg
|
| short ton |
sh tn
|
≡ 2000 lb
|
= 907.184 74 kg
|
| tonne (mts unit) |
t
|
|
≡ 1000 kg
|
| long ton |
long tn or ton
|
≡ 2240 lb
|
= 1016.046 908 8 kg
|
| barge |
|
≡ 22 ½ sh tn
|
= 20,411.656 65 kg
|
| Zentner |
Ztr.
|
|
Definitions vary; see [2] and [3]. See also discussion at Talk:Conversion of units#Zentner
|
In physics, the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf). It should not be read as the mongrel unit "pound metre".
Time
Time, t
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
| second |
s
|
|
(SI base unit)
|
| Planck time |
|
≡ √(Gℏ/c5)
|
≈ 1.351 211 818 x 10-43 s
|
| atomic unit of time |
au
|
≡ a0/(α·c)
|
≈ 2.418 884 254 x 10-17 s
|
| svedberg |
S
|
≡ 10−13 s
|
= 100 fs
|
| shake |
|
≡ 10−8 s
|
= 10 ns
|
| sigma |
|
≡ 10−6 s
|
= 1 μs
|
| jiffy |
|
≡ 1/60 s
|
≈ 16.666 667 ms
|
| jiffy (alternate) |
|
≡ 1/100 s
|
≈ 10 ms
|
| helek |
|
≡ 1/1080 h
|
≈ 3.333333 s
|
| minute |
min
|
|
≡ 60 s
|
| moment |
|
≡ 90 s
|
≡ 90 s
|
| ke(traditional) |
|
≡ 1/100 d
|
≡ 864 s
|
| quarter (of an h) |
ke
|
≡ 1/96 d
|
≡ 900 s
|
| hour |
h
|
≡ 60 min
|
= 3600 s
|
| day |
d
|
≡ 24 h
|
= 86 400 s
|
| week |
wk
|
≡ 7 d
|
= 604 800 s
|
| fortnight |
|
≡ 2 wk
|
= 1 209 600 s
|
| month (hollow) |
mo
|
≡ 29 d
|
= 2 505 600 s
|
| month |
mo
|
≡ 30 d
|
= 2 592 000 s
|
| month (full) |
mo
|
≡ 31 d
|
= 2 678 400 s
|
| year (Calendar) |
a or y
|
≡ 365 d
|
= 31 536 000 s
|
| year (Gregorian) |
a or y
|
≡ 365.2425 d
|
= 31 556 952 s
|
| year (Julian) |
a or y
|
≡ 365.25 d
|
= 31 557 600 s
|
| sidereal year |
a or y
|
≡ 365.256363 d
|
= 31 558 149.76 s
|
| Olympiad |
|
≡ 4 a of 365 d
|
= 1.2614 x 108 s
|
| lustre; lustrum |
|
≡ 5 a of 365 d
|
= 1.5768 x 108 s
|
| octaeteris |
|
≡ 8 a of 365 d
|
= 2.522 88 x 108 s
|
| decade |
|
≡ 10 a of 365 d
|
= 3.1536 x 108 s
|
| enneadecaeteris; Metonic cycle |
|
≡ 110 mo (hollow) + 125 mo (full) = 19 a of 365 d
|
= 5.996 16 x 108 s
|
| Callippic cycle |
|
≡ 441 mo (hollow) + 499 mo (full) = 76 a of 365.25 d
|
= 2.398 377 6 x 108 s
|
| century (Calendar) |
|
≡ 100 a of 365 d
|
= 3.1536 x 108 s
|
| century (Julian) |
|
≡ 100 a of 365.25 d
|
= 3.155 76 x 109 s
|
| Hipparchic cycle |
|
≡ 4 Callippic cycles - 1 d
|
= 9.593 424 x 109 s
|
| millennium (Calendar) |
|
≡ 1000 a of 365 d
|
= 3.1536 x 108 s
|
| millennium (Gregorian) |
|
≡ 1000 a of 365.2425 d
|
= 3.155 695 2 x 1010 s
|
| millennium (Julian) |
|
≡ 1000 a of 365.25 d
|
= 3.155 76 x 1010 s
|
| Sothic cycle |
|
≡ 1461 a of 365 d
|
= 4.607 409 6 x 1010 s
|
Speed
Acceleration
Force
Force, F
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
| newton (SI unit) |
N
|
≡ kg·m/s²
|
|
| atomic unit of force |
au
|
≡ me·α²·c²/a0
|
≈ 8.238 722 241Template:E N
|
| dyne (cgs unit) |
dyn
|
≡ g·cm/s²
|
ljm = 10−5 N
|
| gravet |
|
≡ g × 1 g
|
= 9.806 65 mN
|
| poundal |
pdl
|
≡ 1 lb·ft/s²
|
= 0.138 254 954 376 N
|
| ounce-force |
ozf
|
≡ g × 1 oz
|
= 0.278 013 850 953 781 2 N
|
| pound-force |
lbf
|
≡ g × 1 lb
|
= 4.448 221 615 260 5 N
|
| kilogram-force; kilopond; grave |
kgf; kp
|
≡ g × 1 kg
|
= 9.806 65 N
|
| sthene (mts unit) |
sn
|
≡ 1 t·m/s²
|
= 1 kN
|
| kip; kip-force |
kip; kipf; klbf
|
≡ g × 1000 lb
|
= 4.448 221 615 260 5 kN
|
| ton-force |
tnf
|
≡ g × 1 sh tn
|
= 8.896 443 230 521 kN |
Pressure or mechanical stress
Pressure, p (lower case)
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
| pascal (SI unit) |
Pa
|
≡ N/m²
|
= kg/(m·s²)
|
| barye (cgs unit) |
|
≡ 1 dyn/cm²
|
= 0.1 Pa
|
| poundal per square foot |
pdl/sq ft
|
≡ 1 pdl/sq ft
|
≈ 1.488 164 Pa
|
| millimetre of water (3.98 °C) |
mmH2O
|
≈ 999.972 kg/m³ × 1 mm × g
|
= 9.806 38 Pa (= 0.999972 kgf/m²)
|
| pound per square foot |
psf
|
≡ 1 lb/sq ft × g
|
≈ 47.880 259 Pa
|
| centimetre of water (3.98 °C) |
cmH2O
|
≈ 999.972 kg/m³ × 1 cm × g
|
= 98.0638 Pa
|
| torr |
torr
|
≡ 101 325/760 Pa
|
≈ 133.322 368 4 Pa
|
| millimetre of mercury |
mmHg
|
≡ 13 595.1 kg/m³ × 1 mm × g ≈ 1 torr
|
= 133.322 387 415 Pa
|
| inch of water (3.98 °C) |
inH2O
|
≈ 999.972 kg/m³ × 1 in × g
|
= 249.082 Pa
|
| pièze (mts unit) |
pz
|
≡ 1000 kg/m·s²
|
= 1 kPa
|
| centimetre of mercury |
cmHg
|
≡ 13 595.1 kg/m³ × 1 cm × g
|
= 1.333 223 874 15 kPa
|
| foot of water (3.98 °C) |
ftH2O
|
≈ 999.972 kg/m³ × 1 ft × g
|
= 2.988 98 kPa
|
| inch of mercury |
inHg
|
≡ 13 595.1 kg/m³ × 1 in × g
|
= 3.386 388 640 341 kPa
|
| pound per square inch |
psi
|
≡ 1 lb × g / 1 sq in
|
≈ 6.894 757 kPa
|
| foot of mercury |
ftHg
|
≡ 13 595.1 kg/m³ × 1 ft × g
|
= 40.636 663 684 091 9 kPa
|
| short ton per square foot |
|
≡ 1 sh tn × g / 1 sq ft
|
≈ 95.760 518 kPa
|
| atmosphere (technical) |
atm
|
≡ 1 kgf/cm²
|
= 98.0665 kPa
|
| bar |
bar
|
|
≡ 105 Pa
|
| atmosphere (standard) |
atm
|
|
≡ 101 325 Pa
|
| kip per square inch |
ksi
|
≡ 1 kipf/sq in
|
≈ 6.894757 MPa
|
| kilogram-force per square millimetre |
kgf/mm²
|
≡ 1 kgf/mm²
|
= 9.806 65 MPa
|
Energy, work, or heat
Energy, E
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
| joule (SI unit) |
J
|
≡ N·m = W·s = V·A·s
|
= kg·m²/s²
|
| electronvolt |
eV
|
≡ e × 1 V
|
≈ 1.602 176 x 10-19 J
|
| rydberg |
Ry
|
≡ R∞·ℎ·c
|
≈ 2.179 872 x 10-18 J
|
| hartree |
Eh
|
≡ me·α²·c² (= 2 Ry)
|
≈ 4.359 744 x 10-18 J
|
| atomic unit of energy |
au
|
≡ Eh ≈ 4.359 744 x 10-18 J |
| erg (cgs unit) |
erg
|
≡ 1 g·cm²/s²
|
= 10−7 J
|
| foot-poundal |
ft pdl
|
≡ 1 lb·ft²/s²
|
= 4.214 011 009 380 48 x 10-2 J
|
| cubic centimetre of atmosphere; standard cubic centimetre |
cc atm; scc
|
≡ 1 atm × 1 cm³
|
= 0.101 325 J
|
| inch-pound force |
in lbf
|
≡ g × 1 lb × 1 in
|
= 0.112 984 829 027 616 7 J
|
| foot-pound force |
ft lbf
|
≡ g × 1 lb × 1 ft
|
= 1.355 817 948 331 400 4 J
|
| calorie (20 °C) |
cal20 °C
|
|
≈ 4.1819 J
|
| calorie (thermochemical) |
calth
|
|
≡ 4.184 J
|
| calorie (15 °C) |
cal15 °C
|
|
≡ 4.1855 J
|
| calorie (International Table) |
calIT
|
|
≡ 4.1868 J
|
| calorie (mean) |
calmean
|
|
≈ 4.190 02 J
|
| calorie (3.98 °C) |
cal3.98 °C
|
|
≈ 4.2045 J
|
| litre-atmosphere |
l atm; sl
|
≡ 1 atm × 1 L
|
= 101.325 J
|
| gallon-atmosphere (U.S.) |
US gal atm
|
≡ 1 atm × 1 gal (US)
|
= 383.556 849 013 8 J
|
| gallon-atmosphere (Imperial) |
US gal atm
|
≡ 1 atm × 1 gal (Imp)
|
= 460.632 569 25 J
|
| British thermal unit (thermochemical) |
BTUth
|
≡ 1 lb/g × 1 calth × 1 °F/°C = 9.489 152 380 4 ÷ 9 kJ
|
≈ 1.054 350 kJ
|
| British thermal unit (ISO) |
BTUISO
|
|
≡ 1.0545 kJ
|
| British thermal unit (63 °F) |
BTU63 °F
|
|
≈ 1.0546 kJ
|
| British thermal unit (60 °F) |
BTU60 °F
|
|
≈ 1.054 68 kJ
|
| British thermal unit (59 °F) |
BTU59 °F
|
|
≡ 1.054 804 kJ
|
| British thermal unit (International Table) |
BTUIT
|
≡ 1 lb/g × 1 calIT × 1 °F/°C
|
= 1.055 055 852 62 kJ
|
| British thermal unit (mean) |
BTUmean
|
|
≈ 1.055 87 kJ
|
| British thermal unit (39 °F) |
BTU39 °F
|
|
≈ 1.059 67 kJ
|
| Celsius heat unit (International Table) |
CHUIT
|
≡ 1 BTUIT × 1 °C/°F
|
= 1.899 100 534 716 kJ
|
| cubic foot of atmosphere; standard cubic foot |
cu ft atm; scf
|
≡ 1 atm × 1 ft³
|
= 2.869 204 480 934 4 kJ
|
| kilocalorie; large calorie |
kcal; Cal
|
≡ 1000 calIT
|
= 4.1868 kJ
|
| cubic yard of atmosphere; standard cubic yard |
cu yd atm; scy
|
≡ 1 atm × 1 yd³
|
= 77.468 520 985 228 8 kJ
|
| cubic foot of natural gas |
|
≡ 1000 BTUIT
|
= 1.055 055 852 62 MJ
|
| horsepower-hour |
hp·h
|
≡ 1 hp × 1 h
|
= 2.6845 MJ
|
| kilowatt-hour; Board of Trade Unit |
kW·h; B.O.T.U.
|
≡ 1 kW × 1 h
|
= 3.6 MJ
|
| thermie |
th
|
≡ 1 McalIT
|
= 4.1868 MJ
|
| therm (U.S.) |
|
≡ 100 000 BTU59 °F
|
= 105.4804 MJ
|
| therm (E.C.) |
|
≡ 100 000 BTUIT
|
= 105.505 585 262 MJ
|
| ton of TNT |
tTNT
|
≡ 1 Gcalth
|
= 4.184 GJ
|
| barrel of oil equivalent |
bboe
|
≈ 5.8 MBTU59 °F
|
≈ 6.12 GJ
|
| ton of coal equivalent |
TCE
|
≡ 7 Gcalth
|
= 29.3076 GJ
|
| ton of oil equivalent |
TOE
|
≡ 10 Gcalth
|
= 41.868 GJ
|
| quad |
|
≡ 1015 BTUIT
|
= 1.055 055 852 62 EJ
|
Power
Power, P
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
| watt (SI unit) |
W
|
≡ J/s = N·m/s
|
= kg·m²/s³
|
| lusec |
lusec
|
≡ 1 L·µmHg/s
|
≈ 1.333 x 10-4 W
|
| foot-pound-force per hour |
ft lbf/h
|
≡ 1 ft lbf/h
|
≈ 3.766 161 x 10-4 W
|
| atmosphere cubic centimetre per minute |
atm ccm
|
≡ 1 atm × 1 cm³/min
|
= 1.688 75 x 10-3 W
|
| foot-pound-force per minute |
ft lbf/min
|
≡ 1 ft lbf/min
|
= 2.259 696 580 552 334x 10-2 W
|
| atmosphere–cubic centimetre per second |
atm ccs
|
≡ 1 atm × 1 cm³/s
|
= 0.101 325 W
|
| BTU (International Table) per hour |
BTUIT/h
|
≡ 1 BTUIT/h
|
≈ 0.293 071 W
|
| atmosphere–cubic foot per hour |
atm cfh
|
≡ 1 atm × 1 cu ft/h
|
= 0.797 001 244 704 W
|
| foot-pound-force per second |
ft lbf/s
|
≡ 1 ft lbf/s
|
= 1.355 817 948 331 400 4 W
|
| litre-atmosphere per minute |
L·atm/min
|
≡ 1 atm × 1 L/min
|
= 1.688 75 W
|
| calorie (International Table) per second |
calIT/s
|
≡ 1 calIT/s
|
= 4.1868 W
|
| BTU (International Table) per minute |
BTUIT/min
|
≡ 1 BTUIT/min
|
≈ 17.584 264 W
|
| atmosphere-cubic foot per minute |
atm·cfm
|
≡ 1 atm × 1 cu ft/min
|
= 47.820 074 682 24 W
|
| square foot equivalent direct radiation |
sq ft EDR
|
≡ 240 BTUIT/h
|
≈ 70.337 057 W
|
| litre-atmosphere per second |
L·atm/s
|
≡ 1 atm × 1 L/s
|
= 101.325 W
|
| horsepower (metric) |
hp
|
≡ 75 m kgf/s
|
= 735.498 75 W
|
| horsepower (European electrical) |
hp
|
≡ 75 kp·m/s
|
= 736 W
|
| horsepower (Imperial mechanical) |
hp
|
≡ 550 ft lbf/s
|
= 745.699 871 582 270 22 W
|
| horsepower (Imperial electrical) |
hp
|
|
≡ 746 W
|
| ton of air conditioning |
|
≡ 1 t × 1005 J/kg × 1 °F/K ÷ 10 min
|
= 844.2 W
|
| poncelet |
p
|
≡ 100 m kgf/s
|
= 980.665 W
|
| BTU (International Table) per second |
BTUIT/s
|
≡ 1 BTUIT/s
|
= 1.055 055 852 62Template:E W
|
| atmosphere-cubic foot per second |
atm cfs
|
≡ 1 atm × 1 cu ft/s
|
= 2.869 204 480 934 4Template:E W
|
| ton of refrigeration (IT) |
|
≡ 1 BTUIT × 1 sh tn/lb ÷ 10 min/s
|
≈ 3.516 853Template:E W
|
| ton of refrigeration (Imperial) |
|
≡ 1 BTUIT × 1 lng tn/lb ÷ 10 min/s
|
≈ 3.938 875Template:E W
|
| boiler horsepower |
bhp
|
≈ 34.5 lb/h × 970.3 BTUIT/lb
|
≈ 9.810 657Template:E W
|
Angular momentum
Action, Angular momentum, L, J
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
| SI unit |
J·s
|
|
≡ kg·m²/s
|
| atomic unit of action |
au
|
≡ ℏ = ℎ/2π
|
≈ 1.054 571 596 x 10-34 J·s
|
| cgs unit |
erg·s
|
|
= 10−7 J·s
|
Electric current
Electric charge
Electromotive force
Electrical resistance
Dynamic viscosity
Kinematic viscosity
Information entropy
Information entropy, H
| Name of unit
|
Symbol
|
Definition
|
Relation to SI units
|
| SI unit |
J/K
|
|
≡ 1 J/K
|
| nat; nip; nepit |
nat
|
≡ kB
|
= 1.3806505(23) × 10−23 J/K
|
| bit; shannon |
bit; b; Sh
|
≡ ln(2) × kB
|
= 9.569940(16) × 10−24 J/K
|
| ban; hartley |
ban; Hart
|
≡ ln(10) × kB
|
= 3.1790653(53) × 10−23 J/K
|
| nibble |
|
≡ 4 bits
|
= 3.8279760(64) × 10−23 J/K
|
| byte |
B
|
≡ 8 bits
|
= 7.655952(13) × 10−23 J/K
|
| kilobyte (kibibyte) |
KB; KiB
|
≡ 1024 B
|
= 7.839695(13) × 10−23 J/K
|
Temperature
Software tools
Units and measurements can be easily converted using software tools, but only if the units are explicitly defined and the conversion is compatible (e.g., cmHg to kPa).
One popular command-line utility is units. Another utility and programming library is UDUNITS.
References
- Klein, Herbert. 1988. The science of measurement: A historical survey. New York: Dover Publications.
See also
External links
- ↑ 1.0 1.1 Cite error: Invalid
<ref> tag; no text was provided for refs named nbs
- ↑ The Swiss Federal Office for Metrology gives Zentner on a German language web page[1] and quintal on the English translation of that page[2]; the unit is marked "spécifiquement suisse !"
- ↑ Rowlett, Russ. A Dictionary of Units of Measurement. Viewed October 14, 2006 at http://www.unc.edu/~rowlett/units/dictZ.html