How this works
1 pound = 0.45359237 kg exactly (defined by the 1959 international yard-and-pound agreement). Useful for converting US/UK body weights, gym plates, recipe ingredients, and shipping quotes when the source uses pounds and you need metric for a form, prescription, or label.
The formula
For mental conversion, divide pounds by 2.2 — gives ~0.2% error. So 150 lb ÷ 2.2 ≈ 68 kg (actual 68.04). The exact factor 0.45359237 has lots of decimals because it sits between two unrelated definitions (kg and lb) that didn't share a common root before 1959.
Example calculation
- 1 lb = 0.454 kg
- 10 lb = 4.536 kg
- 50 lb = 22.68 kg (US domestic checked-bag limit)
- 180 lb = 81.65 kg
Frequently asked questions
Is "lb" really the abbreviation for "pound"?
Yes, but it comes from Latin "libra" (the Roman unit of weight, also where the £ symbol comes from). The English "pound" descended from libra via Old English "pund". So "lb" abbreviates the Latin word and "pound" the Germanic-route descendant — same unit, two etymological threads.
How do I convert lb-and-oz together?
Convert everything to ounces first (× 16 for pounds), then multiply by 0.0283495 for kg directly. 8 lb 6 oz = (8 × 16 + 6) × 0.0283495 = 134 × 0.0283495 ≈ 3.798 kg. The all-pairs Weight Converter handles any combination if you'd rather not do the arithmetic by hand.