International System of Units SI
| SI base units | ||
| Base quantity | Name | Symbol |
| length | meter | m |
| mass | kilogram | kg |
| time | second | s |
| electric current | ampere | A |
| thermodynamic temperature | kelvin | K |
| amount of substance | mole | mol |
| luminous intensity | candela | cd |
| Conversion of SI units into British units | |||
|
Quantity |
Conversion Factor |
||
| length |
1 km |
= |
0·6214 mile = 3281 feet |
|
1m |
= |
3·281 feet = 39·37 inches |
|
|
1 mm |
= |
0·03937 inches |
|
| area |
1 km2 |
= |
247·1 acres |
|
1 m2 |
= |
10·76 ft2 |
|
|
1 mm2 |
= |
0·00155 in2 |
|
| volume |
1 m3 |
= |
35·32 ft3 |
|
1 dm3 |
= |
0·03532 ft3 |
|
|
1 litre |
= |
0·2200 gal |
|
| mass; weight |
1 kg |
= |
2·205 lb |
|
1 g |
= |
0·03527 oz |
|
|
density |
1 kg/m3 |
= |
0·06243 lb/ft3 |
| velocity |
1 km/h |
= |
0·6214 mile/h |
|
1 m/s |
= |
3·281 ft/s |
|
|
force |
1 N |
= |
0·2248 Ibf |
|
pressure |
1 kN/m2 |
= |
0·1450 lbf/in2 = 20·88 Ibf/ft2 |
|
temperature |
9/5 °C+32 |
= |
°F |
|
power |
1 kW |
= |
1·341 hp |
|
heat flow rate |
1 W |
= |
3·412 Btu/h |
| energy |
1 J |
= |
0·7376 ft Ibf |
|
1 U |
= |
0·2778 Wh |
|
|
1 MJ |
= |
0·3726 hp h |
|
| quantity of heat |
1 MJ |
= |
0·2778 kWh |
|
1 kJ |
= |
0·9479 Btu |
|
|
heat content |
1 kJ/kg |
= |
0·4299 Btu/lb |
|
specific heat |
1 kJ/kg°C |
= |
0·2388 Btu/lbºF |
|
thermal conductivity |
1 W/m°C |
= |
6·935 Btu in/ft2hºF |
|
thermal conductance |
1 W/m2ºC |
= |
0·1761 Btu/ft2hºF |
| Prefixes | |||
| 10 exp 24 | yotta | Y | 1.000.000.000.000.000.000.000.000 |
| 10 exp 21 | zetta | Z | 1.000.000.000.000.000.000.000 |
| 10 exp 18 | exa | E | 1.000.000.000.000.000.000 |
| 10 exp 15 | peta | P | 1.000.000.000.000.000 |
| 10 exp 12 | tera | T | 1.000.000.000.000 |
| 10 exp 9 | giga | G | 1.000.000.000 |
| 10 exp 6 | mega | M | 1.000.000 |
| 10 exp 3 | kilo | k | 1.000 |
| 10 exp 2 | hecto | h | 100 |
| 10 | deka | da | 10 |
| 1 | 1 | ||
| 10 exp -1 | deci | d | 0.1 |
| 10 exp -2 | centi | c | 0.01 |
| 10 exp -3 | milli | m | 0.001 |
| 10 exp -6 | micro | u | 0.000 001 |
| 10 exp -9 | nano | n | 0.000 000 001 |
| 10 exp -12 | pico | p | 0.000 000 000 001 |
| 10 exp -15 | femto | f | 0.000 000 000 000 001 |
| 10 exp -18 | atto | a | 0.000 000 000 000 000 001 |
| 10 exp -21 | zepto | z | 0.000 000 000 000 000 000 001 |
| 10 exp -24 | yocto | y | 0.000 000 000 000 000 000 000 001 |
| some SI derived unit | Name | Symbol |
| area | square meter | m2 |
| volume | cubic meter | m3 |
| speed, velocity | meter per second | m/s |
| acceleration | meter per second squared | m/s2 |
| wave number | reciprocal meter | m-1 |
| mass density | kilogram per cubic meter | kg/m3 |
| specific volume | cubic meter per kilogram | m3/kg |
| current density | ampere per square meter | A/m2 |
| magnetic field strength | ampere per meter | A/m |
| amount-of-substance concentration | mole per cubic meter | mol/m3 |
| luminance | candela per square meter | cd/m2 |
| mass fraction | kilogram per kilogram, which may be represented by the number 1 | kg/kg = 1 |
| SI derived units with special names and symbols | ||||
| SI derived unit | Name | Unit | Units | Units |
| frequency | Hertz | Hz | - | s-1 |
| power, radiant flux | Watt | W | J/s | m2·kg·s-3 |
| electric charge, quantity of electricity | Coulomb | C | - | s·A |
| electric potential difference, electromotive force |
Volt | V | W/A | m2·kg·s-3·A-1 |
| capacitance | Farad | F | C/V | m-2·kg-1·s4·A2 |
| electric resistance | Ohm | V/A | m2·kg·s-3·A-2 | |
| electric conductance | Siemens | S | A/V | m-2·kg-1·s3·A2 |
| force | Newton | N | - | m·kg·s-2 |
| pressure, stress | Pascal | Pa | N/m2 | m-1·kg·s-2 |
| energy, work, quantity of heat | Joule | J | N·m | m2·kg·s-2 |
| magnetic flux | Weber | Wb | V·s | m2·kg·s-2·A-1 |
| magnetic flux density | Tesla | T | Wb/m2 | kg·s-2·A-1 |
| inductance | Henry | H | Wb/A | m2·kg·s-2·A-2 |
| luminous flux | Lumen | lm | cd·sr (c) | m2·m-2·cd = cd |
| illuminance | Lux | lx | lm/m2 | m2·m-4·cd = m-2·cd |