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Convert lb to kg
1 lb = 0.45359237 kg
Type a value in pounds and the answer in kilograms appears as you go. The conversion is exactly 0.45359237 kg to the pound, and it happens on your own machine — this page asks nothing of a server once it has loaded.
Where it runs
In your browser. The number you type is never part of a request.
Exact by definition
1 lb is exactly 0.45359237 kg — a definition, not a rounded factor.
Answers as you type
No button, no wait. The worked answer is already on the page before any script runs.
Pound and Kilogram
A pound is exactly 0.45359237 kilograms by the same 1959 agreement that fixed the inch. The abbreviation "lb" comes from libra, the Roman unit it descends from.
The kilogram was the last unit defined by a physical object — a cylinder in a vault near Paris that was slowly losing mass. Since 2019 it has been fixed to the Planck constant instead.
Pound to Kilogram in practice
50 lb is 22.68 kg
— a US bag of cement.
20 lb is 9.072 kg
— a large sack of dog food.
Pound to Kilogram at a glance
| lb | kg |
|---|---|
| 1 | 0.45359237 |
| 2 | 0.90718474 |
| 3 | 1.36077711 |
| 5 | 2.26796185 |
| 10 | 4.5359237 |
| 20 | 9.0718474 |
| 50 | 22.6796185 |
| 100 | 45.359237 |
Convert lb to kg: common questions
How many kilograms are in a pound?
Exactly 0.45359237. One pound is 0.45359237 kilograms, and the box above will do it for any figure you type.
Is this conversion exact, or rounded?
The ratio is exact. It is not a rounded constant typed into a table: it is derived from the definitions of the two units, so it agrees with any other correct converter to as many digits as you care to compare.
Why does another converter show a slightly different number?
Almost always rounding rather than disagreement. Many converters cut the answer to two or four decimals, and some carry a factor that was rounded before the multiplication rather than after. The figures here are computed from the exact definitions and only rounded on the way to the screen.
Where these figures come from
The claims this page makes about weight units are checkable, and these are the documents that settle them.
How this page works
The factor is a constant in the page and the arithmetic is four operations, so nothing is sent anywhere and nothing needs to be. The number you type never leaves the browser — there is no request for it to travel in.