Weight & Mass Converter
Convert a weight or mass between twelve units, from the microgram up to the tonne, spanning both metric and imperial systems. Strictly, weight and mass are different quantities — mass is the amount of matter, weight is the force gravity exerts on it — but in everyday use the pound and the kilogram are treated as interchangeable measures of the same thing, and that is how this converter works. Every factor derives from the exact 1959 definition of one pound as 0.45359237 kilograms.
How to use this tool
- Type the weight you want to convert into the Value field. Decimals and scientific notation such as 2.5e3 are accepted.
- Pick the unit your number is currently in from the From menu.
- Pick the unit you want the answer in from the To menu.
- Read the result as you type — there is no button to press.
- Switch on “Show every equivalent unit” to see the same weight in all twelve units at once.
The formula
Mass uses the kilogram as its base unit. The pound has been defined as exactly 0.45359237 kilograms since 1959, which makes every derived imperial mass exact as well.
kilograms = value × kg_per_unit
result = kilograms ÷ kg_per_target- kg_per_unit
- Kilograms in one unit of the input
- kg_per_target
- Kilograms in one unit of the output
Mass and weight are different quantities. These units measure mass, which does not change with gravity. A kilogram is a kilogram on the Moon; its weight is not.
Worked examples
Kilograms to pounds for body weight
- Given
- 10 kilograms
- Result
- 22.046226 pounds
10 kg ÷ 0.45359237 kg per pound = 22.046226 lb. The pound has been defined as exactly 0.45359237 kg since 1959, so this is exact, not an approximation.
Stone and pounds
- Given
- 11 stone
- Result
- 154 pounds
One stone is exactly 14 pounds, so 11 × 14 = 154 lb (about 69.85 kg). Stone remains common for body weight in the UK and Ireland.
Ounces to grams for cooking
- Given
- 8 ounces
- Result
- 226.796185 grams
8 oz × 28.349523 g per ounce = 226.80 g. The avoirdupois ounce is one sixteenth of a pound.
Frequently asked questions
Mass is the amount of matter in an object and does not change with location; weight is the force gravity exerts on that mass and varies with gravity. On the Moon your mass is unchanged but your weight is about a sixth of Earth’s. In everyday use the two are conflated, and units like the kilogram and pound are used for both — which is how this converter treats them.
No. A US ton (short ton) is 2,000 pounds, while an imperial ton (long ton) is 2,240 pounds — about 12% heavier. The metric tonne is different again at 1,000 kilograms (about 2,204.6 pounds). This converter keeps all three distinct so you do not mix them up.
One kilogram is about 2.2046226 pounds, because a pound is defined as exactly 0.45359237 kilograms. For a rough mental conversion, doubling the kilograms and adding ten percent gets you close.
A carat is a unit of mass used for gemstones, equal to exactly 200 milligrams (0.2 grams). It is not to be confused with karat, which measures gold purity. This converter includes the carat for gem weights.
Yes. Every factor derives from exact definitions — the pound as 0.45359237 kg, the ounce as one sixteenth of that, and so on — so no rounding error is introduced. Only the final displayed figure is rounded for readability.
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