How to use the weight converter
Enter a number in the Value box, pick the unit you have and the unit you need, then press Convert. The swap button reverses the direction, so you can check a result the other way round without retyping anything.
Under the main answer a table shows the same weight in all nine supported units: milligrams, grams, kilograms, metric tonnes, ounces, pounds, stones, US short tons and UK long tons.
How the conversion works
The pound has been defined in terms of the kilogram since 1959, and every other imperial unit is a fixed multiple of the pound:
- 1 pound (lb) = 0.45359237 kg exactly
- 1 ounce (oz) = 1/16 lb = 28.349523125 g
- 1 stone (st) = 14 lb = 6.35029318 kg
- 1 US short ton = 2,000 lb = 907.18474 kg
- 1 UK long ton = 2,240 lb = 1,016.0469088 kg
- 1 metric tonne = 1,000 kg
The converter turns your value into a tiny common base unit and then into the target unit, so these exact relationships are kept and only the final display is rounded.
Worked example
To convert 70 kg to pounds: 70 / 0.45359237 = 154.323584 lb (rounded to six decimals). Going the other way, 154.323584 lb × 0.45359237 brings you back to 70 kg.
Good to know
- Weight here means mass, which is what kitchen scales, bathroom scales and shipping labels report.
- The ounce used is the everyday avoirdupois ounce. Troy ounces, used for precious metals, are slightly heavier and are not included.
- The word "ton" is ambiguous: a US short ton (2,000 lb) is lighter than a UK long ton (2,240 lb), and both differ from the metric tonne (1,000 kg, about 2,204.6 lb).
- Stones are still common in the UK and Ireland for body weight. 11 st is 154 lb, or about 69.85 kg.
- Results show up to six decimals; very small values appear in scientific notation, such as 9.84207e-10.
- Negative weights are rejected. Zero is accepted.