The exact factor, and a shortcut you can do in your head
kilograms = pounds × 0.453592, pounds = kilograms × 2.20462
The pound is defined as exactly 0.45359237 kg. For a fast estimate, halve the pounds, then subtract 10%: 180 lb → 90 − 9 = 81 kg, close to the exact 81.6. Dividing by 2.2 gets you there too, just slightly high.
Quick reference — 100 to 300 lb
| Pounds | Kilograms |
|---|---|
| 100 lb | 45.4 kg |
| 120 lb | 54.4 kg |
| 150 lb | 68.0 kg |
| 170 lb | 77.1 kg |
| 180 lb | 81.6 kg |
| 200 lb | 90.7 kg |
| 250 lb | 113.4 kg |
| 300 lb | 136.1 kg |
Medicine works in kilograms because doses are set per kg of body weight, and BMI needs kg. 150 lb is 68 kg, so at 1.70 m that is a BMI of 23.5.
Two shortcuts, and why one is closer
- Divide by 2.2. Simple, but runs about 1% high: 200 lb ÷ 2.2 = 90.9 kg against the exact 90.7.
- Halve, then take off 10%. Closer: 200 → 100 − 10 = 90 kg. Both land within a couple of percent, so either is fine for everyday use.
- Mass, not weight. Kilograms and pounds both measure mass here, so the conversion is the same anywhere — on Earth, the Moon, or a plane.
Common questions
How many kilograms are in a pound?
One pound is 0.453592 kilograms. The value is exact: the avoirdupois pound is defined as precisely 0.45359237 kg.
How do I convert pounds to kg in my head?
Divide by 2, then take off 10% of that. For 180 lb: half is 90, minus 9 is 81 kg (the exact answer is 81.6). Dividing by 2.2 also works and is close.
What is 150 pounds in kilograms?
150 pounds is 68.04 kg. That is a common adult body weight and a value doctors use to work out weight-based drug doses.
