How many kilograms are in a pound?

1 pound = 0.45359237 kilograms. In the other direction, 1 kilogram = 2.204622622 pounds.

The international avoirdupois pound is defined as exactly 0.45359237 kilograms, agreed by the United States, United Kingdom and four other Commonwealth nations in 1959. Every imperial mass unit derives from it.

The kilogram is the SI base unit of mass. Since 2019 it has been defined by fixing the Planck constant, replacing the platinum-iridium cylinder held near Paris that had served as the standard since 1889.

Is a 23 kg bag the same as a 50 lb bag?

Almost. 23 kg is 50.7 lb, so a 50 lb limit is slightly stricter than a 23 kg one.

Unit-To-Unit Weight conversion

Pounds to Kilograms

1 pound = 0.45359237 kilograms

This is the most-searched unit conversion in the world, and the only one on this page defined by international treaty rather than derivation. The 1959 agreement fixed the pound at 0.45359237 kg exactly, ending a century in which the US and British pounds differed in the sixth decimal place.

Formula kg = lb × 0.45359237

Pound (lb) max 24 digits

Kilogram (kg) max 24 digits

Type in either field — the other updates on every keystroke. Need other units? Open the full weight converter.

Pounds to Kilograms — quick reference
Pound	Kilogram
1 lb	0.453592 kg
2 lb	0.907185 kg
3 lb	1.360777 kg
4 lb	1.814369 kg
5 lb	2.267962 kg
10 lb	4.535924 kg
15 lb	6.803886 kg
20 lb	9.071847 kg
25 lb	11.339809 kg
50 lb	22.679619 kg
100 lb	45.359237 kg
500 lb	226.796185 kg
1000 lb	453.59237 kg

Kilograms to Pounds — reverse
Kilogram	Pound
1 kg	2.204623 lb
2 kg	4.409245 lb
3 kg	6.613868 lb
4 kg	8.81849 lb
5 kg	11.023113 lb
10 kg	22.046226 lb
15 kg	33.069339 lb
20 kg	44.092452 lb
25 kg	55.115566 lb
50 kg	110.231131 lb
100 kg	220.462262 lb
500 kg	1102.311311 lb
1000 kg	2204.622622 lb

Worked examples

Common values
Situation	From	To
Newborn baby	8.5 lb	3.86 kg
Airline checked-bag limit	50 lb	22.68 kg
Standard gym plate	45 lb	20.41 kg
Adult body weight	150 lb	68.04 kg
Loaded barbell	225 lb	102.06 kg

Mental-math shortcut

Halve the pounds, then subtract a tenth of that half. For 150 lb: 75 minus 7.5 gives 67.5 kg, against an exact 68.04 kg, within about 1%.

Where this conversion comes up

Airlines, gyms and clinics all meet here. Many airlines cap economy checked bags at 23 kg, which is 50.7 lb. US gym plates are in pounds, so a 45 lb plate is 20.41 kg, not 20. Outside the US, doctors record weight in kilograms and calculate many medicine doses per kilogram. Carriers round shipping weights up, so convert generously.

Common mistakes

Multiplying by 2.2 instead of 0.4536 goes in the wrong direction. Avoirdupois pounds also differ from troy pounds (373.24 g), and the symbol is lb, not lbs.

Background

Pounds varied by region and trade for centuries. In 1959 the US, UK, Canada, Australia, New Zealand and South Africa fixed the international pound at exactly 0.45359237 kg. Before that the US and British pounds differed by about one part in a million, small but enough to matter in precision work.

Learn more

Frequently asked

How many kilograms are in a pound?: 1 pound = 0.45359237 kilograms. In the other direction, 1 kilogram = 2.204622622 pounds.
What is a pound?: The international avoirdupois pound is defined as exactly 0.45359237 kilograms, agreed by the United States, United Kingdom and four other Commonwealth nations in 1959. Every imperial mass unit derives from it.
What is a kilogram?: The kilogram is the SI base unit of mass. Since 2019 it has been defined by fixing the Planck constant, replacing the platinum-iridium cylinder held near Paris that had served as the standard since 1889.
Is a 23 kg bag the same as a 50 lb bag?: Almost. 23 kg is 50.7 lb, so a 50 lb limit is slightly stricter than a 23 kg one.

Related weight conversions

Kilograms to Pounds Ounces to Grams Grams to Ounces Stones to Pounds Kilograms to Stones Pounds to Ounces Grams to Kilograms