How it works
Kilograms are the metric unit of mass used almost everywhere, while pounds are still used in the United States and, for body weight, in the UK. Since 1959 the international avoirdupois pound has been defined as exactly 0.45359237 kg, so the conversion is exact in one direction and a fixed decimal in the other.
The formula
lb = kg ÷ 0.45359237 ≈ kg × 2.20462262 kg = lb × 0.45359237Worked example. A 70 kg person weighs 70 ÷ 0.45359237 = 154.32 lb. A 23 kg airline suitcase allowance is 23 × 2.20462262 = 50.71 lb — airlines round it to 50 lb. Going the other way, 180 lb × 0.45359237 = 81.65 kg.
Quick reference table
| Kilograms | Pounds | Pounds | Kilograms |
|---|---|---|---|
| 1 kg | 2.2046 lb | 1 lb | 0.4536 kg |
| 2 kg | 4.4092 lb | 2 lb | 0.9072 kg |
| 5 kg | 11.0231 lb | 5 lb | 2.268 kg |
| 10 kg | 22.0462 lb | 10 lb | 4.5359 kg |
| 20 kg | 44.0925 lb | 20 lb | 9.0718 kg |
| 23 kg | 50.7063 lb | 23 lb | 10.4326 kg |
| 30 kg | 66.1387 lb | 30 lb | 13.6078 kg |
| 50 kg | 110.2311 lb | 50 lb | 22.6796 kg |
| 60 kg | 132.2774 lb | 60 lb | 27.2155 kg |
| 70 kg | 154.3236 lb | 70 lb | 31.7515 kg |
| 80 kg | 176.3698 lb | 80 lb | 36.2874 kg |
| 100 kg | 220.4623 lb | 100 lb | 45.3592 kg |
Quick mental shortcut
Double the kilograms and add 10%: 70 kg → 140 + 14 = 154 lb. It is within about 0.2% of the exact answer. To go back, halve the pounds and subtract 10% of the result: 154 lb → 77 − 7.7 ≈ 69.3 kg (exact: 69.85 kg), so it is a little less accurate in that direction.
In the UK, body weight is often given in stones and pounds: 1 stone = 14 lb = 6.35 kg, so 70 kg is 11 st 0.3 lb. Ounces are 1/16 of a pound (28.35 g). For grams, ounces and tonnes, use the full unit converter.
Checking your weight? The BMI calculator accepts pounds directly, and the ideal weight calculator shows healthy ranges.