Lbs to Kg Converter
Convert pounds to kilograms with the exact factor 1 lb = 0.45359237 kg. Enter pounds and get kilograms, grams, and stone — handy for body weight, luggage limits, and shipping.
Example: with Weight in pounds 150 → Kilograms: 68.04 kg.
- In grams68,039 g
- In stone10.71 stone
Computed by the calculator below using its default values. Change any input to see your own numbers.
kg = lb × 0.45359237, exact by definition since 1959. The quick mental version: halve the pounds, then knock off about 10 percent.
Why the factor is exactly 0.45359237
Since the international agreement of 1959, the avoirdupois pound has been defined as exactly 0.45359237 kilograms — the pound is literally a metric unit in disguise. Multiply pounds by that factor and the answer is exact: 150 lb is 68.04 kg, 220 lb is 99.79 kg. Dividing by 2.20462 gives the same result from the other direction.
For mental math, halve the pounds and subtract 10 percent of that half: 150 lb → 75 → about 67.5 kg, within half a kilo of the true 68.04. That beats the common divide-by-2 shortcut, which overstates weight by about 10 percent — enough to matter at airline luggage counters, where a 50 lb allowance is 22.7 kg, not 25.
How it’s calculated
Kilograms = pounds × 0.45359237 (exact NIST definition of the avoirdupois pound). Grams = kg × 1,000, rounded to the nearest gram. Stone = pounds ÷ 14, the UK body-weight convention.
Converts mass units only — pound-force in engineering contexts is a force, not a weight on a scale, and follows different rules.
Pounds to kilograms, common body weights
| Pounds | Kilograms | Stone |
|---|---|---|
| 100 lb | 45.36 kg | 7.14 st |
| 125 lb | 56.7 kg | 8.93 st |
| 150 lb | 68.04 kg | 10.71 st |
| 175 lb | 79.38 kg | 12.5 st |
| 200 lb | 90.72 kg | 14.29 st |
| 250 lb | 113.4 kg | 17.86 st |
Computed with 1 lb = 0.45359237 kg exactly and 1 stone = 14 lb; rounded to two decimals.
Common mistakes
- Dividing pounds by 2 flat — that inflates the metric weight about 10 percent (150 lb is 68 kg, not 75).
- Using 2.2 as an exact factor on large loads; 1,000 lb is 453.6 kg, while lb ÷ 2.2 claims 454.5.
- Entering a weight that includes ounces as decimals — 150 lb 8 oz is 150.5 lb, not 150.8.
- Confusing stone (14 lb) with pounds when reading UK weights.
Frequently asked questions
What is the formula for lbs to kg?
Kilograms = pounds × 0.45359237. The factor is exact by definition, so 150 lb × 0.45359237 = 68.04 kg. Dividing by 2.20462 is the same operation.
Is 1 kg equal to 2.2 lbs?
Approximately. One kilogram is 2.20462 lb, so 2.2 is fine for rough estimates but drifts on bigger numbers — a 23 kg checked bag is 50.7 lb, right at many airline limits.
How many kg is 150 pounds?
68.04 kg. Halve 150 to get 75, subtract about 10 percent (7.5), and you land near 67.5 — the exact multiplication gives 68.0.
What is a stone?
A UK unit of body weight equal to 14 pounds. So 150 lb is 10 stone 10, usually written 10 st 10 lb. This converter shows decimal stone alongside kilograms.