Tables showing the SI equivalents of metric units and some older units commonly used for mass, length, speed, area, volume, force, pressure, energy, and power
Units of Mass Table
| Unit | SI equivalent | Inverse |
|---|---|---|
| 1 oz (ounce) | equals 2.835 x 10-2 kg | 1 kg = 35.27 oz |
| 1 lb (pound) | equals 0.4536 kg | 1 kg = 2.205 lb |
| 1 ton (= 2240 lb) | equals 1016 kg | 1 kg = 0.9842 x 10-3 ton |
| 1 short ton (=2000 lb) | equals 907 kg | 1 kg = 1.102 x 10-3 short tons |
| 1 t (tonne) | equals 1000 kg | 1 kg = 10-3 t |
| 1 u (unified mass unit) | equals 1.660 x 10-27 kg | 1 kg = 6.024 x 1026 u |
The Royal Society (1975) Quantities, Units and Symbols, London, The Royal Society
Units of Length Table
| Unit | SI equivalent | Inverse |
|---|---|---|
| 1 mm (millimetre) | equals 1 x 10-3 m | 1 m = 1000 mm |
| 1 cm (centimetre) | equals 1 x 10-2 | 1 m = 100 cm |
| 1 m (metre) | equals 1 m | 1 m = 1 m |
| 1 km (kilometre) | equals 1000 m | 1 m = 0.001 km |
| 1 in (inch) | equals 2.540 x 10-2 m | 1 m = 39.37 in |
| 1 ft (foot) | equals 0.3048 m | 1 m = 3.281 ft |
| 1 yd (yard) | equals 0.9144 m | 1 m = 1.094 yd |
| 1 mi (mile) | equals 1.609 x 103 m | 1 m = 6.214 x 10-4 mi |
| 1 NM (nautical mile) | equals 1852 m | 1 m = 5.399568 x 10-4 Nm |
| 1 mil (Mil) | equals 2.54 x 10-5 m | 1 m = 39370.078740157 mil |
Units of Speed Table
| Unit | SI equivalent | Inverse |
|---|---|---|
| 1 km h-1 (kph) | equals 0.2778 m s-1 | 1 m s-1 = 3.600 kph |
| 1 mi h-1 (mph) | equals 0.4470 m s-1 | 1 m s-1 = 2.237 mph |
The Royal Society (1975) Quantities, Units and Symbols, London, The Royal Society
Units of Area Table
| Unit | SI equivalent | Inverse |
|---|---|---|
| 1 ft2 | equals 6.452 x 10 -4 m 2 | 1 m2 = 1550 in2 |
| 1 ft2 | equals 9.290 x 10-2 m2 | 1 m2 = 10.76 ft2 |
| 1 yd2 | equals 0.8361 m2 | 1 m2 = 1.196 yd2 |
| 1 acre | equals 4047 m2 | 1 m2 = 2.471 x 10-4 acre |
| 1 ha (hectare) | equals 104 m2 | 1 m2 = 10-4 ha |
| 1 mi2 | equals 2.590 x 106m2 | 1 m2 = 3.861 x 10-7 mi2 |
The Royal Society (1975) Quantities, Units and Symbols, London, The Royal Society
Units of Volume Table
| Unit | SI equivalent | Inverse |
|---|---|---|
| 1 in3 | equals 1.639 x 10-5 m3 | 1 m3 = 6.102 x 104 in3 |
| 1 ft3 | equals 2.832 x 10-2 m3 | 1 m3 = 35.31 ft3 |
| 1 yd3 | equals 0.7646 m3 | 1 m3 = 1.308 yd3 |
| 1 litre | equals 10-3 m3 | 1 m3 = 1000 litres |
| 1 gallon (UK) | equals 4.546 litres | 1 m3 = 220.0 gallons (UK) |
| 1 gallon (US) | equals 3.785 litres | 1 m3 = 264.2 gallons (US) |
| 1 barrel | equals 159 litres | 1 m3 = 6.3 barrels |
| 1 bushel | equals 3.637 x 10-2 m3 | 1 m3 = 27.50 bushels |
The Royal Society (1975) Quantities, Units and Symbols, London, The Royal Society
Units of Force Table
| Unit | SI equivalent | Inverse |
|---|---|---|
| 1 kgf (weight of 1 kg mass) | equals 9.807 N | 1 N = 0.102 kgf |
| 1 lbf (weight of 1 lb mass) | equals 4.448 N | 1 N = 0.2248 lbf |
The Royal Society (1975) Quantities, Units and Symbols, London, The Royal Society
Units of Pressure Table
| Unit | SI equivalent | Inverse |
|---|---|---|
| 1 bar (≈1 atmosphere) | equals 105 Pa (pascals) | 1 Pa = 10-5 bar |
| 1 kgf m-2 | equals 9.807 Pa | 1 Pa = 0.102 kgf m-2 |
| 1 lbf in-2 (or psi) | equals 6.895 Pa | 1 Pa = 1.450 x 10-4 psi |
The Royal Society (1975) Quantities, Units and Symbols, London, The Royal Society
Units of Energy Table
| Unit | SI equivalent | Inverse |
|---|---|---|
| 1 barrel of oil equivalent (boe) | equals 5.7 GJ (lower heating value) | 1 GJ = 0.175 boe |
| 1 cal (calorie) | equals 4.2 J | 1 J = 0.24 cal |
| 1 ft lb (foot pound) | equals 1.356 J | 1 J = 0.7375 ft lb |
| 1 eV (electron-volt) | equals 1.602 x 10-19 J | 1 J = 6.242 x 1018 eV |
| 1 MeV | equals 1.602 x 10-13 J | 1 J = 6.242 x 1012 MeV |
The Royal Society (1975) Quantities, Units and Symbols, London, The Royal Society
Units of Power Table
| Unit | SI equivalent | Inverse |
|---|---|---|
| 1 HP (horse power) | equals 745.7 W | 1 W = 1.341 x 10-3 HP |
The Royal Society (1975) Quantities, Units and Symbols, London, The Royal Society