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How Many Kilograms in a Pound?
That first figure isn't an approximation, incidentally — since 1959 the pound has been defined as exactly 0.45359237 kilograms by international agreement.
The formulas
Pounds → kilograms: divide by 2.2046, or multiply by 0.4536
Kilograms → pounds: multiply by 2.2046
Conversion table
| Pounds | Kilograms |
|---|---|
| 1 lb | 0.45 kg |
| 5 lb | 2.27 kg |
| 10 lb | 4.54 kg |
| 20 lb | 9.07 kg |
| 25 lb | 11.34 kg |
| 50 lb | 22.68 kg |
| 100 lb | 45.36 kg |
| 150 lb | 68.04 kg |
| 200 lb | 90.72 kg |
| Kilograms | Pounds |
|---|---|
| 1 kg | 2.20 lb |
| 5 kg | 11.02 lb |
| 10 kg | 22.05 lb |
| 20 kg | 44.09 lb |
| 50 kg | 110.23 lb |
| 70 kg | 154.32 lb |
| 100 kg | 220.46 lb |
Quick mental maths. You rarely need four decimal places:
- Pounds to kilograms: halve it, then take off 10%. 160 lb → 80 → minus 8 → 72 kg. (True answer 72.6 — close enough for most purposes.)
- Kilograms to pounds: double it, then add 10%. 70 kg → 140 → plus 14 → 154 lb. (True answer 154.3.)
These two tricks are accurate to within about 1% and are worth committing to memory.
Where each is used. The kilogram is the SI base unit of mass and is standard almost everywhere. The pound remains in everyday use in the United States, and in the UK it persists alongside metric for body weight and some food. The UK also uses stones for body weight — 1 stone = 14 pounds = 6.35 kg — which is why a British person may describe their weight as "11 stone 4".
Related units
| Unit | Equals |
|---|---|
| 1 pound (lb) | 16 ounces |
| 1 ounce (oz) | 28.35 grams |
| 1 kilogram | 1,000 grams |
| 1 stone | 14 lb = 6.35 kg |
| 1 US ton | 2,000 lb = 907.18 kg |
| 1 metric tonne | 1,000 kg = 2,204.6 lb |
Why "lb"? The abbreviation comes from the Latin libra pondo, meaning "a pound by weight" — which is also where the pound sterling and the £ sign originate. It's why the abbreviation contains letters the English word doesn't.
Mass versus force — the technical footnote. Strictly, the kilogram measures mass while the pound is used both as a unit of mass (pound-mass) and of force (pound-force, lbf). In everyday use nobody distinguishes them, and on Earth the numbers line up. It matters in engineering and physics, where 1 lbf = 4.448 newtons. If you're converting a weight on a bathroom scale, ignore this entirely.
A note on precision: for cooking, luggage and body weight, 2.2 is fine. For shipping quotes, dosing calculations or engineering, use 2.20462 — the rounding error compounds quickly at larger figures. Converting 500 lb with 2.2 rather than 2.2046 puts you off by more than half a kilogram.
Two similar answers: How Many Liters Are in a Gallon? and How Many Miles Is 20,000 Steps?.
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