Pound to Kilogram Converter

One pound is exactly 0.45359237 kilograms. Multiply pounds by 0.453592 for everyday accuracy. So 1.75 lb is 0.7938 kg and 3.5 lb is 1.5876 kg. Going the other way, one kilogram is 2.20462 pounds.

Where the factor comes from

The international yard and pound agreement of 1959 defined the avoirdupois pound as exactly 0.45359237 kg, replacing several slightly different national pounds with one exact value. Every digit is a definition rather than a measurement, so the conversion is exact to as many decimals as you need.

Common values

Estimating in your head

• Halve it. 10 lb → about 5 kg. Quick, roughly 10% high.
• Halve it, then take off 10%. 10 lb → 5 − 0.5 = 4.5 kg, against a true 4.536 kg.
• Going the other way, double and add 10%. 5 kg → 10 + 1 = 11 lb, against a true 11.02 lb.

Common mistake

Using 0.5 as the factor because it is easier. That is a 10% error — on a 20 lb parcel it is nearly a kilogram, which is enough to change a shipping band. Use 0.4536 and round the answer, not the factor.

Also worth knowing: pounds are not the only imperial weight in use. British body weight is usually given in stones and pounds, where one stone is 14 pounds, so a decimal answer in stone is not read the way it looks.

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Quick answer: one pound equals 0.453592 kilograms. So to convert pounds to kilograms, multiply by 0.45359237.

How to convert pounds to kilograms

kilograms = pounds × 0.45359237

The pound has been defined as exactly 0.45359237 kilograms since 1959. Body weight in the US, gym plates, and package weights all speak in pounds.

The kilogram is the SI base unit of mass, since 2019 defined via the Planck constant rather than a physical metal cylinder in Paris.

Pound to Kilogram conversion table

Need the opposite direction? Use the Kilogram to Pound converter, or read our complete guide to weight conversions for every formula in one place.

Where each unit is used

Kilograms are the legal and scientific standard almost everywhere, and the unit every metric scale reports. Pounds persist in the United States for everyday weight, and in the UK and Ireland alongside kilograms — a British scale often shows both, and a British hospital records kilograms while the patient thinks in stones and pounds.

The practical consequence is that this conversion is needed most where accuracy matters: shipping weights against a banded price, dosing by body weight, and baggage allowances where a kilogram over has a fixed cost.

Useful anchors

• 1 kg = 2.2 lb — close enough for mental work, and only 0.005 lb off.
• 10 lb = 4.54 kg, so a 20 lb parcel is just over 9 kg.
• A 23 kg baggage allowance is about 50.7 lb, which is why it is often quoted as "50 lb" and is not quite the same thing.