Convert kilograms to pounds

Body weight, airline baggage and Anglo-American recipes are quoted in pounds. This is the conversion that comes up most when travelling or following a US training plan.

The weight in kilograms is divided by 0.45359237, the exact definition of the avoirdupois pound since the 1959 international agreement.

The pound has also been exact since 1959

The same international agreement that fixed the yard defined the avoirdupois pound as exactly 0.45359237 kilograms. Before then, the British and American pounds differed in their final decimal places, which caused problems in trade and in science.

Not all pounds weigh the same

The troy pound, used for precious metals, is 373.24 grams, considerably less than the avoirdupois 453.59. That is why an ounce of gold does not weigh the same as an ounce of flour: the troy ounce is 31.10 grams and the common ounce 28.35. When buying metals, confirm which is being used.

The British stone

In the United Kingdom and Ireland, body weight is given in stones of fourteen pounds. Someone of 70 kg weighs 11 stone and 0.3 pounds, said as 'eleven stone'. It is a unit that survives only for people: nobody buys potatoes in stones.

Weight and mass are not the same

The kilogram measures mass and does not change with gravity; weight is a force and would change on the Moon. In everyday use the two are treated as synonyms, and bathroom scales show mass even when they say weight.