Convert Pounds to Kilograms
Switch pounds into kilograms for filling in metric forms, calculating gym plate loads, or converting US recipes and grocery weights.
1 lb = 0.453592 kg
One pound equals exactly 0.45359237 kilograms. To convert pounds to kilograms, multiply by 0.45359237 — so 150 lb = 68.04 kg and 200 lb = 90.72 kg. The figure is exact by definition under the 1959 international yard and pound agreement, which defined the avoirdupois pound in terms of the kilogram rather than the other way round. Halving and taking off ten percent is a good mental approximation: 180 lb gives 90 minus 9, about 81 kg against the true 81.6. Two other pounds exist and are not interchangeable — the troy pound used for precious metals is 373.24 g, and the ounce inside it differs too, which is why gold quoted per ounce is not the ounce on a kitchen scale. Airline baggage is the everyday case: a 50 lb allowance is 22.7 kg, and a 23 kg limit is 50.7 lb.
Quick reference: pounds to kilograms
| Pounds | Kilograms |
|---|---|
| 1 | 0.454 kg |
| 10 | 4.536 kg |
| 45 | 20.41 kg |
| 50 | 22.68 kg |
| 100 | 45.36 kg |
| 150 | 68.04 kg |
| 180 | 81.65 kg |
| 200 | 90.72 kg |
| 225 | 102.06 kg |
How do you convert pounds to kilograms?
Formula: kilograms = pounds × 0.45359237 • A 150 lb body weight → 150 × 0.45359237 = 68.04 kg, the figure a metric medical record would show. • A 50 lb airline baggage allowance → 50 × 0.45359237 = 22.68 kg, which is why carriers with a 23 kg limit are effectively matching the US 50 lb standard. • A 45 lb Olympic barbell → 45 × 0.45359237 = 20.41 kg, close to but not the same as the 20 kg metric bar used in international competition.
When and why people use pounds to kilograms
Air travel produces the most frequent need. Checked-baggage allowances are quoted as 50 lb by US carriers and 23 kg by most others, and the two are near-identical by design — but a bag packed to 50 lb exactly is 22.68 kg and will pass a 23 kg limit, while a bag at 23 kg is 50.7 lb and will fail a strict 50 lb one. Healthcare is the second. Medication dosing is calculated per kilogram of body weight almost universally, including in the US, so a weight recorded in pounds has to be converted before a paediatric or oncology dose can be worked out. This is a context where the rounded 2.2 shortcut is not acceptable. Strength training is a third. Barbell plates come in both 45 lb and 20 kg versions, and gyms often mix them. A '225 lb' bench is 102.06 kg, whereas the visually similar metric loading of 100 kg is 220.46 lb — a real difference that matters when comparing lifts.
Common mistakes to watch for when converting pounds to kilograms
Dividing by 2.2 is the standard shortcut and it is 0.8% low, which is harmless for luggage and unacceptable for medication. At 200 lb the shortcut gives 90.91 kg against a true 90.72 kg. The second trap is confusing pounds-mass with pounds-force in engineering contexts, where the same word describes a weight and a force. Third, the UK and Ireland commonly express body weight in stones and pounds, so a figure like '11 stone 4' means 158 lb and must be resolved before converting. Finally, note that some older recipes and apothecary references use the troy pound of 12 troy ounces, which is about 373 g rather than 454 g — an entirely different unit that survives only in precious-metal and pharmaceutical history.
How to estimate pounds to kilograms in your head
Halve the pound figure and then subtract 10% of that halved number. For 150 lb: half is 75, ten percent of 75 is 7.5, giving 67.5 kg against a true 68.04. That is 0.8% low — the same drift as the familiar 'divide by 2.2'. For a closer estimate, halve and subtract 9% instead: 75 minus 6.75 gives 68.25 kg, now only 0.3% high. Anchors: 10 lb ≈ 4.5 kg, 50 lb ≈ 22.7 kg, 100 lb ≈ 45.4 kg, 200 lb ≈ 90.7 kg. The luggage anchor is the most practically useful — a 50 lb allowance is 22.7 kg, so if a scale in kilograms reads under 22.5 you are safely inside a 50 lb limit with margin for the scale's own tolerance.
Pounds to Kilograms FAQ
How many kg is a pound?
- Exactly 0.45359237 kg. The pound is defined in terms of the kilogram, so the conversion is exact.
Is dividing by 2.2 good enough?
- It is 0.8% low. Acceptable for luggage, not acceptable for weight-based medication dosing.
Does a 50 lb bag pass a 23 kg limit?
- Yes — 50 lb is 22.68 kg. The reverse does not hold: 23 kg is 50.7 lb and fails a strict 50 lb limit.
How much is 150 lb in kg?
- 68.04 kg.
Is a 45 lb barbell the same as a 20 kg bar?
- No. A 45 lb bar is 20.41 kg. The difference is small but real when comparing loaded totals.
What does '11 stone 4' mean?
- 11 stones and 4 pounds, which is 158 lb or 71.67 kg. A stone is 14 lb.
What is a troy pound?
- An obsolete unit of about 373 g used for precious metals, entirely different from the 454 g avoirdupois pound.
Is my weight stored anywhere?
- No. The value stays in your browser and is never transmitted.
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Sources: 1959 international yard and pound agreement defining the avoirdupois pound as exactly 0.45359237 kg; NIST Handbook 44; IATA baggage guidance on standard checked allowances.