⚖️ Weight & mass
lbs to kg Converter
Enter pounds, choose kilograms and press Convert. One pound is exactly 0.45359237 kg, so 150 lb is 68.04 kg.
About the lbs to kg Converter
A pound is the smaller unit, so converting lbs to kg always produces a lower number — roughly 45% of it. Because 0.45359237 is an exact definition, not a measurement, the conversion has no rounding error until the display does: this page shows eight significant digits.
Gym plates, boxing weights and US medical records are usually in pounds, while most of the world uses kilograms. Converting 220 lb to 99.79 kg rather than a flat 100 kg is the kind of difference that matters at a weigh-in.
How the calculation works
- Kilograms = pounds × 0.45359237
- Pounds = kilograms × 2.2046226218
- 1 stone = 14 lb = 6.35029318 kg
Reference values
| Pounds | Kilograms | Stones |
|---|---|---|
| 1 lb | 0.4536 kg | 0 st 1.0 lb |
| 10 lb | 4.5359 kg | 0 st 10.0 lb |
| 50 lb | 22.680 kg | 3 st 8.0 lb |
| 100 lb | 45.359 kg | 7 st 2.0 lb |
| 150 lb | 68.039 kg | 10 st 10.0 lb |
| 175 lb | 79.379 kg | 12 st 7.0 lb |
| 200 lb | 90.718 kg | 14 st 4.0 lb |
| 225 lb | 102.058 kg | 16 st 1.0 lb |
Worked examples
- 120 lb × 0.45359237 = 54.43 kg, a common flyweight limit.
- 180 lb is 81.65 kg, and 200 lb is 90.72 kg.
- 250 lb is 113.40 kg, just over the heaviest standard powerlifting class.
Checking the answer by hand
Halve the pounds and subtract a tenth of the result: 180 lb becomes 90, minus 9, which is 81 kg against an exact 81.65 kg. That estimate is within 1% every time, and the gap tells you whether you divided by the right number.
Common mistakes
- Dividing by 2.5 instead of multiplying by 0.4536, which understates the weight by nearly 12%.
- Treating a US short ton (2,000 lb) as a metric tonne (2,204.6 lb), a 9% difference on bulk orders.
- Using a gym scale in pounds and a doctor's scale in kilograms without converting — the same body, two numbers, 2.2 apart.
A last check on the numbers: 37 Pound works out to 16.78 Kilogram, and reversing that with the same factor brings you back to 37 Pound. Because Pound to Kilogram is a single multiplication, any tool that gives a different figure for the same input is rounding somewhere in the middle rather than only at the end.