How to use the weight converter
- Type a number in the From box. Decimals (2.5) and thousands separators (1,250) both work.
- Pick the unit you have in the first menu and the unit you want in the second. The To box and the result line update as you type.
- To work backwards, type in the To box and the From box follows.
- Press Swap units to flip the direction, or read Same weight in every unit to see your number in every other unit at once.
- For body weight in the UK, use Stone and pounds to kilograms: enter the stone and the spare pounds and read the answer in kg.
How the conversion works
Every unit is stored as a size in grams. The tool multiplies your number by the size of the From unit, then divides by the size of the To unit: result = value × From size ÷ To size. The pound is defined as exactly 0.45359237 kg, so 1 oz = 1/16 lb = 28.349523125 g, 1 stone = 14 lb = 6.35029318 kg, a US (short) ton is 2,000 lb and a UK long ton is 2,240 lb. A tonne is 1,000 kg, a troy ounce is 31.1034768 g, a carat is 0.2 g and a grain is 64.79891 mg. The factors match NIST Guide to the SI, Appendix B.8. Answers show up to 8 significant digits.
Strictly, these are units of mass. A scale responds to gravity, which differs by only about 0.5 percent between the equator and the poles, so for everyday use mass and weight are interchangeable. Pound-force and other force units are not covered.
Worked example with the default values
With 1 in the From box, Kilogram (kg) as the From unit and Pound (lb) as the To unit, the result line reads 1 kg = 2.2046226 lb. Under it you see the split 2 lb 3.27 oz (0.2046226 × 16 ounces) and the reverse line 1 lb = 0.45359237 kg. In the stone card, 11 st 4 lb is 158 lb, which is 71.67 kg.
Common weight conversions
| Convert | Result |
|---|---|
| 50 kg | 110.23113 lb |
| 70 kg | 154.32358 lb |
| 100 kg | 220.46226 lb |
| 150 lb | 68.038856 kg |
| 1 oz | 28.349523 g |
| 1 st | 6.3502932 kg |
| 1 US ton | 907.18474 kg |
| 1 oz t | 31.103477 g |
Cooking from grams? The cooking converter turns cups and spoons into grams for flour, sugar, butter and other ingredients, because an ounce of weight is not a fluid ounce. For liquids use the volume converter, for other quantities the unit converter, and to check a result against a health range try the BMI calculator.
Limits and edge cases
Negative numbers convert normally, which suits weight change. The ounce in the menu is the everyday avoirdupois ounce used for food and mail; the troy ounce for gold and silver is listed separately. A comma followed by one or two digits counts as a decimal comma (2,5 is 2.5). Letters and currency symbols are blocked with a hint, and anything above 1e24 is refused. This page converts mass only: going between volume and weight needs a density, which it does not assume.
Sources: NIST Guide to the SI, Appendix B.8; NIST Handbook 44, Appendix C.
Weight converter FAQ
How do I convert kg to lbs?
Multiply the kilograms by 2.2046226. For example, 70 kg × 2.2046226 = 154.32358 lb. To go back, multiply pounds by 0.45359237.
How many pounds are in a stone?
A stone is exactly 14 pounds, or 6.35029318 kg. So 11 stone 4 pounds is 158 lb, which is 71.67 kg.
What is the difference between a US ton, a tonne and a UK long ton?
A US (short) ton is 2,000 lb, or 907.18474 kg. A metric tonne is 1,000 kg, or 2,204.6226 lb. A UK long ton is 2,240 lb, or 1,016.0469 kg. All three are in the unit menus.
What is a troy ounce?
A troy ounce is exactly 31.1034768 grams, about 10 percent heavier than the everyday ounce of 28.349523 grams. Gold, silver and platinum are priced per troy ounce.