Kilograms, pounds and stones without the mental arithmetic

2.20462262185. The pound is defined as exactly 0.45359237 kilograms, so this is an exact conversion rather than a measured one. For a suitcase, doubling and adding a tenth — kg × 2.2 — is about 0.2% low, which on a 20 kg bag is under a tenth of a pound and nowhere near an airline’s tolerance.

Strictly it is mass. Kilograms and pounds measure the amount of matter in a thing, which does not change wherever you take it. Weight is the force gravity pulls that mass with, it is measured in newtons, and it is about six times smaller on the Moon. Everyday language merged the two long ago and bathroom scales are labelled in kilograms, so this page follows the everyday usage — and nothing on it changes if you read every “weight” as “mass”. The distinction only starts to bite in physics problems, where using the wrong one costs you the answer.

Fourteen pounds, or 6.35029318 kg. It survives in the UK and Ireland almost entirely for body weight, where 11 st 4 lb is far more common than 72 kg. Convert the whole figure to pounds before entering it — 11 st 4 lb is 158 lb, which comes out at 71.67 kg.

No, and the spelling is the only warning you get. A metric tonne is 1,000 kg. A US short ton is 2,000 pounds, which is 907.18 kg — about 9% lighter. A UK long ton is 2,240 pounds, or 1,016.05 kg, slightly heavier than the tonne. All three are in the list under their own names, because shipping quotes, freight rates and emissions figures all use one of them and rarely say which.

Sixteen — for ordinary avoirdupois ounces, the ones on food packaging and the ones used on this page, at 28.349523125 g each. Precious metals are sold in troy ounces, which are heavier at 31.1035 g, and there are only twelve of them to a troy pound. So a troy ounce of gold weighs more than an ounce of flour while a troy pound weighs less than an ordinary pound. Do not use this page for bullion.

Because kilo is a prefix, not a unit — it means a thousand of something. In everyday speech it is shorthand for kilogram and that is almost always what is meant, but kilometre and kilojoule are kilos too. The list spells the units out so nothing is ambiguous.

No. The conversion runs in your own browser, there is no server behind this site, and nothing is written to your device. Close the tab and every figure is gone.