Weight & Mass Converter
Convert kilograms to pounds, pounds to stone, grams to ounces and back — with body weights shown properly in stone and pounds.
Fill in the fields to see your result.
Quick reference table
Common weights converted between the two units you've selected. Change either dropdown and the table follows.
Mass, weight, and why nobody minds
Strictly, mass is how much matter something contains and weight is the force gravity applies to it. A kilogram is a unit of mass; a newton is a unit of weight. On the moon your mass is unchanged and your weight is a sixth of what it was.
In every context outside a physics exam this distinction is ignored, and sensibly so. Bathroom scales, luggage limits, recipes and shipping manifests all say "weight" and all mean mass. This converter does the same.
The exact definitions
Like length, the imperial weights are defined in metric terms, so these are exact rather than measured:
| Unit | Exactly equal to |
|---|---|
| 1 pound | 0.45359237 kg (exact, by definition) |
| 1 ounce | 1/16 pound = 28.349523125 g |
| 1 stone | 14 pounds = 6.35029318 kg |
| 1 tonne (metric) | 1,000 kg |
| 1 US ton (short) | 2,000 lb = 907.18474 kg |
| 1 UK ton (long) | 2,240 lb = 1,016.05 kg |
Three tons, and the mess they cause
This is the single most expensive confusion in this whole category. "Ton" means three different things depending on who is writing:
- Short ton — 2,000 lb, about 907 kg. Standard in the United States.
- Long ton — 2,240 lb, about 1,016 kg. The historic British ton, still used in some shipping.
- Tonne (metric ton) — exactly 1,000 kg. Everywhere else.
The gap between a short ton and a tonne is around 10%. On a single shipping container that is hundreds of kilograms. If a quote says "ton" and money depends on it, ask which one they mean before you agree to anything.
Stone: the unit that only measures people
Stone is used in Britain and Ireland for one thing only — body weight — and it's always written as stone and pounds, never as a decimal. Someone is 11 stone 4, not 11.29 stone. There are 14 pounds to a stone, so the same trap as feet and inches applies: 11.5 stone is 11 stone 7 pounds, not 11 stone 5.
Enter a weight in kilograms above and this page gives you the stone-and-pounds reading automatically, because the decimal version is no use to anyone.
Doing it in your head
| Rough rule | Real answer | Error |
|---|---|---|
| kg → lb: double it, add 10% | × 2.2046 | under 0.3% |
| lb → kg: halve it, take off 10% | × 0.4536 | under 0.8% |
| 1 oz ≈ 28 g | 28.35 g | 1.2% |
| 100 g ≈ 3.5 oz | 3.527 oz | 0.8% |
The kg-to-pounds one is worth learning. 70 kg: double to 140, add 14, get 154. The true figure is 154.3. That's accurate enough for a luggage scale, a gym, or an argument.
Frequently asked questions
How many pounds are in a kilogram?
2.20462 pounds, and the relationship is exact in the other direction: a pound is defined as 0.45359237 kilograms. For mental arithmetic, double the kilograms and add 10% — that gets you within a third of a percent.
How do I write my weight in stone and pounds?
Enter it in kilograms above and the stone-and-pounds reading appears at the top of the results. There are 14 pounds to a stone, so decimal stone is misleading: 11.5 stone means 11 stone 7 pounds, not 11 stone 5.
Is a ton the same as a tonne?
No, and the difference matters. A tonne is exactly 1,000 kg. A US short ton is 907 kg and a UK long ton is 1,016 kg. That's a spread of about 10%, which on a shipping quote is real money. All three are in the dropdown so you can compare them directly.
What's the difference between mass and weight?
Mass is how much matter an object contains; weight is the force gravity exerts on that mass. Kilograms and pounds measure mass. Everyday use treats them as the same thing, which is fine everywhere except a physics exam.
Why do recipes sometimes give ounces for liquids?
Because there are two different ounces. A fluid ounce measures volume, an ounce measures weight, and they aren't interchangeable — a fluid ounce of honey weighs far more than a fluid ounce of water. Use our volume converter for fluid ounces; this page handles weight only.
Are my numbers sent anywhere?
No. Everything is calculated inside your own browser. Nothing you type is uploaded, stored or shared, and there's no sign-up.
Related calculators
Please note: CalcuLane uses the internationally agreed definitions, which are exact for length, weight, temperature, volume, speed and data. Shoe sizing is a convention rather than a measurement and varies between brands, so treat those results as a starting point. Where precision genuinely matters, confirm against an authoritative source.