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Weight Converter
Weight Converter
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How weight and mass conversion works
Strictly, these are mass units, not weight units. Mass is how much matter there is; weight is the force gravity exerts on it, which changes with location. A kilogram of flour is a kilogram on the Moon and weighs about a sixth as much there. In everyday use the words are interchangeable, and every converter, including this one, treats them that way.
Like length, the metric-to-imperial factors here are exact by definition. The pound has been defined as exactly 0.453 592 37 kilograms since 1959.
Formulas
Pounds to kilograms
kg = lb × 0.45359237
Ounces to grams
g = oz × 28.349523125
Stone to kilograms
kg = st × 6.35029318
1 stone = 14 pounds.
Worked examples
| From | To | Result |
|---|---|---|
| 1 kg | lb | 2.20462 lb |
| 70 kg | lb | 154.324 lb |
| 150 lb | kg | 68.0389 kg |
| 1 oz | g | 28.3495 g |
| 12 stone | kg | 76.2035 kg |
| 1 US ton | metric ton | 0.907185 metric ton |
Results are computed with the same factors the converter above uses, rounded to six significant figures.
Common weights
| kg | lb | stone |
|---|---|---|
| 1 | 2.20462 | 0.157473 |
| 5 | 11.0231 | 0.787365 |
| 10 | 22.0462 | 1.57473 |
| 50 | 110.231 | 7.87365 |
| 60 | 132.277 | 9.44838 |
| 70 | 154.324 | 11.0231 |
| 80 | 176.37 | 12.5978 |
| 100 | 220.462 | 15.7473 |
Body weight in the UK is normally quoted to the nearest pound within a stone: 70 kg reads as "11 stone 0".
Worth knowing
- 1 pound = 0.453 592 37 kg exactly. 1 ounce = 1/16 pound = 28.349 523 125 g exactly.
- A stone is 14 pounds. It is still the normal unit for body weight in the UK and Ireland and is used nowhere else.
- There are three different tons. A short ton is 2,000 lb (907.185 kg) and is what "ton" means in the US. A long ton is 2,240 lb (1,016.047 kg). A tonne, or metric ton, is exactly 1,000 kg. The short and long ton differ by 12%.
- The troy ounce used for precious metals is 31.103 g, about 10% heavier than the ordinary avoirdupois ounce. Gold prices are quoted in troy ounces.
Frequently asked questions
- What is the difference between mass and weight?
- Mass is the amount of matter in an object and does not change. Weight is the force gravity exerts on that mass and depends on where you are. Kilograms and pounds as used in shops are mass units; the pound-force used in engineering is a weight unit and is a different quantity despite the shared name.
- How many pounds are in a kilogram?
- About 2.2046. The exact relationship runs the other way: a pound is defined as exactly 0.453 592 37 kilograms, so 2.2046 is a rounded reciprocal rather than a defined figure.
- Which ton does a figure mean?
- Unless it says, the number is ambiguous by up to 12%. In American sources "ton" usually means the short ton of 2,000 pounds. In British sources it may mean the long ton of 2,240 pounds. "Tonne" always means exactly 1,000 kilograms, which is the safest form to write.
- Why is a troy ounce different from a normal ounce?
- They descend from separate medieval systems. The troy system survived only for precious metals and gemstones, where it never made sense to switch. A troy ounce is 31.103 grams against the ordinary ounce's 28.350, so a "12 ounce" gold figure is about 10% more metal than the same number of ordinary ounces.