This provides a summary of most of the units of measurement to be found in use around the world today, together with the appropriate conversion factors needed to change them into a 'standard' SI unit.

To change | into | do this | To change | into | do this |
---|---|---|---|---|---|

acres | hectares | x 0.4047 | kilograms | ounces | x 35.3 |

acres | sq. kilometres | / 247 | kilograms | pounds | x 2.2046 |

acres | sq. metres | x 4047 | kilograms | tonnes | / 1000 # |

acres | sq. miles | / 640 # | kilograms | tons (UK/long) | / 1016 |

barrels (oil) | cubic metres | / 6.29 | kilograms | tons (US/short) | / 907 |

barrels (oil) | gallons (UK) | x 34.97 | kilometres | metres | x 1000 # |

barrels (oil) | gallons (US) | x 42 # | kilometres | miles | x 0.6214 |

barrels (oil) | litres | x 159 | litres | cubic inches | x 61.02 |

centimetres | feet | / 30.48 # | litres | gallons (UK) | x 0.2200 |

centimetres | inches | / 2.54 # | litres | gallons (US) | x 0.2642 |

centimetres | metres | / 100 # | litres | pints (UK) | x 1.760 |

centimetres | millimetres | x 10 # | litres | pints (US liquid) | x 2.113 |

cubic cm | cubic inches | x 0.06102 | metres | yards | / 0.9144 # |

cubic cm | litres | / 1000 # | metres | centimetres | x 100 # |

cubic cm | millilitres | x 1 # | miles | kilometres | x 1.609 |

cubic feet | cubic inches | x 1728 # | millimetres | inches | / 25.4 # |

cubic feet | cubic metres | x 0.0283 | ounces | grams | x 28.35 |

cubic feet | cubic yards | / 27 # | pints (UK) | litres | x 0.5683 |

cubic feet | gallons (UK) | x 6.229 | pints (UK) | pints (US liquid) | x 1.201 |

cubic feet | gallons (US) | x 7.481 | pints (US liquid) | litres | x 0.4732 |

cubic feet | litres | x 28.32 | pints (US liquid) | pints (UK) | x 0.8327 |

cubic inches | cubic cm | x 16.39 | pounds | kilograms | x 0.4536 |

cubic inches | litres | x 0.01639 | pounds | ounces | x 16 # |

cubic metres | cubic feet | x 35.31 | square cm | sq. inches | x 0.1550 |

feet | centimetres | x 30.48 # | square feet | sq. inches | x 144 # |

feet | metres | x 0.3048 # | square feet | sq. metres | x 0.0929 |

feet | yards | / 3 # | square inches | square cm | x 6.4516 # |

fl.ounces (UK) | fl.ounces (US) | x 0.961 | square inches | square feet | / 144 # |

fl.ounces (UK) | millilitres | x 28.41 | square km | acres | x 247 |

fl.ounces (US) | fl.ounces (UK) | x 1.041 | square km | hectares | x 100 # |

fl.ounces (US) | millilitres | x 29.57 | square km | square miles | x 0.3861 |

gallons | pints | x 8 # | square metres | acres | / 4047 |

gallons (UK) | cubic feet | x 0.1605 | square metres | hectares | / 10 000 # |

gallons (UK) | gallons (US) | x 1.2009 | square metres | square feet | x 10.76 |

gallons (UK) | litres | x 4.54609 # | square metres | square yards | x 1.196 |

gallons (US) | cubic feet | x 0.1337 | square miles | acres | x 640 # |

gallons (US) | gallons (UK) | x 0.8327 | square miles | hectares | x 259 |

gallons (US) | litres | x 3.785 | square miles | square km | x 2.590 |

grams | kilograms | / 1000 # | square yards | square metres | / 1.196 |

grams | ounces | / 28.35 | tonnes | kilograms | x 1000 # |

hectares | acres | x 2.471 | tonnes | tons (UK/long) | x 0.9842 |

hectares | square km | / 100 # | tonnes | tons (US/short) | x 1.1023 |

hectares | square metres | x 10000 # | tons (UK/long) | kilograms | x 1016 |

hectares | square miles | / 259 | tons (UK/long) | tonnes | x 1.016 |

hectares | square yards | x 11 960 | tons (US/short) | kilograms | x 907.2 |

inches | centimetres | x 2.54 # | tons (US/short) | tonnes | x 0.9072 |

inches | feet | / 12 # | yards | metres | x 0.9144 # |

**x** means 'multiply by'
**/** means 'divide by'
**#** means it is an exact value

All other values given to an appropriate degree of accuracy.

Taken from
A Dictionary of Measures, Units & Conversions by *Frank Tapson*