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Weight Converter
Convert a mass between metric and imperial units. Choose the starting unit and the target unit, and the same quantity is also listed in every other unit below.
How each mass unit is defined
The kilogram is the base unit of mass. Since 2019 it has been defined by fixing the Planck constant at 6.62607015 × 10−34 joule-seconds, replacing the old platinum-iridium cylinder. Every other unit in the converter is a fixed multiple of it.
- 1 pound = 0.45359237 kg exactly (1959 agreement)
- 1 ounce = 1/16 pound = 28.349523125 g exactly
- 1 stone = 14 pounds = 6.35029318 kg exactly
- 1 short ton = 2,000 pounds = 907.18474 kg
- 1 long ton = 2,240 pounds = 1,016.0469088 kg
- 1 metric tonne = 1,000 kg
- 1 troy ounce = 31.1034768 g exactly
- 1 metric carat = 200 mg
Three kinds of ton and two kinds of ounce
The word "ton" is the biggest source of mistakes. The US short ton is 2,000 lb, the UK long ton is 2,240 lb, and the metric tonne is 1,000 kg. They differ by roughly 10% from each other, so a shipping weight quoted in "tons" should always be checked for which one is meant.
Ounces split in a similar way. The ordinary (avoirdupois) ounce of about 28.35 g is used for food and post, while the troy ounce of about 31.10 g is used for precious metals. A troy ounce is therefore roughly 9.7% heavier. Do not use the ordinary ounce for gold, silver or platinum quantities.
Mass is not weight
Strictly, kilograms and pounds measure mass, the amount of matter, while weight is a force that depends on local gravity. Kitchen and bathroom scales are calibrated to show mass under normal Earth gravity, so for everyday use the two words are interchangeable. A person who weighs 70 kg on Earth has the same mass on the Moon, even though a spring scale there would read about one sixth as much.
For engineering work that needs a force, use the force converter and the newton instead.
Stone and pounds, and quick estimates
Body weight in the UK is often given in stone and pounds. To convert 11 st 4 lb, first change it to pounds (11 × 14 + 4 = 158 lb) and then enter 158 as pounds. The result is about 71.67 kg.
For quick mental estimates, multiply kilograms by 2.2 to get pounds, or halve pounds and subtract a tenth of that to get kilograms. Roughly 100 g is 3.5 oz, and one ounce is about 28 g. Use the exact figures for dosing, postage or trade.
Typical uses include luggage allowances, postage bands, recipe scaling, gym plates in pounds against kilogram plates, and reading product labels from another country. Always check the unit printed on the source before converting.
Worked example
A parcel scale reads 70 kilograms. What is that in pounds?
Inputs
| Value | 70 |
|---|---|
| From | Kilograms (kg) |
| To | Pounds (lb) |
Result
70 kg = 154.323584 lb
| Milligrams (mg) | 70,000,000 |
|---|---|
| Grams (g) | 70,000 |
| Metric tonnes (t) | 0.07 |
| Ounces (avoirdupois) (oz) | 2,469.1773 |
| Stone (st) | 11.023113 |
| Short tons (US) (short ton) | 0.07716179 |
| Long tons (UK) (long ton) | 0.06889446 |
| Troy ounces (oz t) | 2,250.5523 |
| Carats (metric) (ct) | 350,000 |
- Factors are exact definitions where one exists; results are shown to about six significant digits.
Accuracy note: Factors use the standard definitions stated on this page. Results are rounded for display; for engineering or legal work use the full-precision factors.
Frequently asked questions
How many pounds are in a kilogram?
One kilogram is about 2.2046226 pounds. The exact relationship is 1 lb = 0.45359237 kg, so divide kilograms by that figure to get pounds.
How many grams are in an ounce?
An avoirdupois ounce is 28.349523125 grams. A troy ounce, used for precious metals, is 31.1034768 grams.
What is a stone in kilograms?
One stone is 14 pounds, which is exactly 6.35029318 kilograms. A body weight given as 12 stone is therefore about 76.2 kilograms.
Which ton does the converter use?
It lists the metric tonne, the US short ton and the UK long ton separately, so you can choose the one that matches your source.
What is a carat?
The metric carat used for gemstones is 200 milligrams. It is unrelated to the karat that describes gold purity.
Related calculators
More conversion references
For weight and mass conversion tables beyond this tool, see PakMath weight and mass conversion tables. PakMath is a sister project of Adzita.