EngineeringFormulaMass Conversion
Convert lb to kg
1 lb = 0.45359 kg
Nearly every material weight, shipping spec, or load rating in US practice is given in pounds, while essentially all engineering calculation and international specifications use kilograms.
The pound is defined by international agreement (1959) as exactly 0.45359237 kilograms - unlike most unit conversions on this page, this factor isn't derived from other constants, it's the definition itself.
A 100 lb bag of concrete mix weighs about 45.4 kg - the figure that would appear on the same product's metric packaging.
Reference Table
| pounds (lb) | kilograms (kg) |
|---|---|
| 1 | 0.45359 |
| 5 | 2.268 |
| 10 | 4.5359 |
| 25 | 11.34 |
| 50 | 22.68 |
| 100 | 45.359 |
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Frequently Asked Questions
Is this the same pound used for force (lbf)?
No - this conversion is for pound-mass (lb), a unit of mass. Pound-force (lbf) is a related but distinct unit of force, equal to the weight of one pound-mass under standard Earth gravity (about 4.448 N). The two are easy to conflate in US customary work since both are casually called "pounds."
Is a US ton the same as a metric tonne?
No - a US (short) ton is 2,000 lb, about 907 kg; a metric tonne is exactly 1,000 kg, about 2,205 lb; and a UK (long) ton, less commonly used today, is 2,240 lb, about 1,016 kg. All three are called "tons" or close to it, but they differ by several percent, enough to matter on a large shipment.
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