How weight conversion works
Like the inch, the pound has had an exact metric definition since 1959: one avoirdupois pound is exactly 0.45359237 kilograms. So converting kg to lbs — or lbs back to kg — is exact arithmetic, and the familiar factor 2.20462 is just 1 ÷ 0.45359237 rounded. This converter works both directions and also breaks every weight into stones and pounds (the UK format), ounces, and grams.
The formula
Here kg is the mass in kilograms, pounds is the avoirdupois pound, and a stone is exactly 14 pounds.
Worked examples — both directions
kg → lbs: 70 kg ÷ 0.45359237 = 154.32 lb, which in UK terms is 11 st 0.3 lb.
lbs → kg: 150 lb × 0.45359237 = 68.04 kg — or 10 st 10 lb.
Common weights quick reference
| Kilograms | Pounds | Stones & pounds |
|---|---|---|
| 50 kg | 110.2 lb | 7 st 12.2 lb |
| 60 kg | 132.3 lb | 9 st 6.3 lb |
| 70 kg | 154.3 lb | 11 st 0.3 lb |
| 80 kg | 176.4 lb | 12 st 8.4 lb |
| 90 kg | 198.4 lb | 14 st 2.4 lb |
| 100 kg | 220.5 lb | 15 st 10.5 lb |
The stone, explained for American readers
If a British friend says they weigh "eleven stone six", they mean 11 stones plus 6 pounds: 11 × 14 + 6 = 160 lb. The stone survives in the UK and Ireland purely for body weight — groceries are in kilograms, luggage allowances in kilograms, but people are in stones. One quirk worth knowing: because a stone is 14 lb (not 10 or 16), losing "a stone" is a bigger deal than it sounds to American ears — it's a 14-pound loss. And for fast kg → lbs mental math anywhere in the world: double the kilograms, then add 10% of that. 90 kg → 180 + 18 = 198 lb; the exact answer is 198.4 lb.