What this calculator does
Mass and weight are technically different things (mass is how much matter something contains, weight is the force gravity exerts on it), but in everyday use, and in every unit this calculator handles, the two are treated the same, as they are on any bathroom or kitchen scale.
Every unit converts through the kilogram as a base, so an obscure pairing like ounces to stone works exactly the same way as gram to kilogram: multiply into kilograms, then divide back out into the target unit.
The formula
Metric mass units differ from each other by clean powers of ten. Imperial units do not: a pound is defined as exactly 0.453592 kilograms, and a stone, at 14 pounds, comes to 6.35029 kg. The US short ton (2,000 lb) and UK long ton (2,240 lb) are different units entirely despite the shared name, which is a common source of error in freight and shipping figures.
| Term | Meaning |
|---|---|
| Base unit | The kilogram, which every other unit converts through. |
| Stone | 14 pounds, or about 6.35 kg: used mainly for body weight in the UK and Ireland. |
| Short ton / long ton | The US ton (2,000 lb, ≈907 kg) and UK ton (2,240 lb, ≈1,016 kg): different units, not regional spellings of the same one. |
The inputs explained
| Field | What to enter |
|---|---|
| Value | The value to convert. |
| From | The unit you are converting from. |
| To | The unit you want the answer in. |
When to use it
Converting body weight between kilograms, pounds and stone
Medical, fitness and everyday contexts each favour a different unit depending on the country: this handles all three the same way, through the shared kilogram base.
Reading a recipe or ingredient list in another system
A US recipe in ounces and pounds converted to grams and kilograms, or the reverse, needs exact factors rather than rough approximations to keep proportions right.
Checking freight or shipping weight in tons
US short tons and UK long tons differ by about 11 per cent: a difference large enough to matter on a shipping manifest or a weighbridge docket, and easy to miss since both are just called "tons".
Converting a small mass, like a dose or a component
Milligrams and grams cover the lighter end, pharmaceutical doses, jewellery, and small parts, using the same base-unit method as the heavier units.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
One of each unit, converted to kilograms
A single unit from milligrams to UK tons, each converted to kilograms to compare true scale.
| From | In kilograms |
|---|---|
| Milligram | 0.000001 kg |
| Gram | 0.001 kg |
| Tonne | 1,000 kg |
| Ounce | 0.0283495 kg |
| Pound | 0.453592 kg |
| Stone | 6.35029 kg |
| US short ton | 907.185 kg |
| UK long ton | 1,016.05 kg |
Converting 75 kg to other units
A single body-weight figure of 75 kilograms expressed across the other common units.
Questions
How many pounds are in a stone?
Exactly 14. A stone is a British and Irish unit still used for body weight, equal to 6.35029 kg.
What is the difference between a US ton and a UK ton?
A US short ton is 2,000 lb (about 907 kg); a UK long ton is 2,240 lb (about 1,016 kg): roughly 11 per cent heavier. Neither matches the metric tonne (1,000 kg) exactly, which is a third, separate unit again.
Is mass the same as weight?
Technically no (mass is an amount of matter, weight is the gravitational force on that mass), but every unit in everyday use, including all the ones here, treats them interchangeably, since gravity is effectively constant at the Earth’s surface.
How many grams are in an ounce?
About 28.35 g, from the exact factor 0.0283495 kg per ounce. This is the avoirdupois ounce used for general weight, not the slightly heavier troy ounce used for precious metals.
Why do UK weights sometimes get shown in stone and pounds together?
It is a traditional compound format, like feet and inches for height: a weight of 75 kg might be given as "11 stone 8" rather than 11.8 stone, splitting off the leftover pounds after whole stone.
For height alongside weight in the same imperial-metric split, see the height and weight converter. For volume, use the volume and capacity converter.