Pounds to kilograms (lb to kg)

The formula

kg = lb × 0.45359237

Where the factor comes from — each unit by its definition, then its size in SI:

• 1 lb = 0.45359237 × kg = 0.45359237 kg
• 1 kg is the SI unit of mass.

Dividing the two SI sizes gives the factor: 0.45359237, exact — every step above is a definition, not a measurement. The reverse factor is 2.20462262185.

Physics formulas take mass in kilograms. Pounds (lb) are a unit of mass; pound-force (lbf) is the weight of a pound — a different quantity, on the force page.

Worked examples

• A family car: 3,306.93 lb = 1,500 kg — 3,306.93 × 0.45359237 = 1,500
• An adult: 165.347 lb = 75 kg — 165.347 × 0.45359237 = 75
• A bag of flour: 1 lb = 0.453592 kg — 1 × 0.45359237 = 0.453592
• A block of butter (250 g): 0.551156 lb = 0.25 kg — 0.551156 × 0.45359237 = 0.25

Frequently asked questions