Weight Converter
Convert between metric, US and imperial weight units, from milligrams to tons. The pound is defined as exactly 0.45359237 kg.
How weight conversion works
Result = Value × (kg per “from” unit) ÷ (kg per “to” unit)
Example: 250 grams to ounces is 0.25 ÷ 0.028349523125 = 8.818490487 oz, so a 250 g pack is a little under 9 ounces.
The exact definitions used
The international avoirdupois pound is defined as exactly 0.45359237 kilograms. The ounce is 1/16 pound, the stone is 14 pounds, the US short ton is 2000 pounds and the UK long ton is 2240 pounds. The metric tonne is 1000 kg.
| Unit | In kilograms | Defined as |
|---|---|---|
| 1 ounce (oz) | 0.028349523125 kg | 1/16 lb |
| 1 pound (lb) | 0.45359237 kg | International definition |
| 1 stone (st) | 6.35029318 kg | 14 lb |
| 1 US short ton | 907.18474 kg | 2000 lb |
| 1 UK long ton | 1016.0469088 kg | 2240 lb |
| 1 metric tonne (t) | 1000 kg | SI (megagram) |
Handy reference values
| From | To |
|---|---|
| 1 kg | 2.204622622 lb |
| 1 lb | 453.59237 g |
| 1 oz | 28.34952313 g |
| 100 g | 3.527396195 oz |
| 1 stone | 6.35029318 kg |
| 1 US ton | 0.90718474 tonnes |
Weight and mass
In everyday language “weight” means how heavy something is, measured in kilograms or pounds; strictly speaking that is mass. Scientists reserve “weight” for the force of gravity on an object, measured in newtons. Kitchen scales, bathroom scales and shipping labels all report mass, so this converter handles mass units.
Common questions
Are UK and US pounds the same?
Yes. Both countries use the international pound of exactly 0.45359237 kg, and the same 16-ounce avoirdupois ounce. The difference is in tons: a US “ton” is 2000 lb, a UK “ton” is 2240 lb, and a metric tonne is 1000 kg (about 2204.6 lb).
Is a fluid ounce the same as an ounce?
No. A fluid ounce measures volume, an ounce measures weight. One US fluid ounce of water weighs about 1.04 oz, but for other liquids and for dry ingredients the relationship is different. Use the volume converter for fluid ounces.
What about troy ounces for gold?
Precious metals are weighed in troy ounces of exactly 31.1034768 g, which is heavier than the ordinary ounce. This converter uses the ordinary (avoirdupois) ounce only.
Sources
- Unit Conversion (SP 811 Appendix B factors and Handbook 44 Appendix C tables), National Institute of Standards and Technology (NIST)
- Weights and Measures Act 1985, Schedule 1 (definitions of imperial units), legislation.gov.uk