Pounds to Kilograms
Convert pounds to kilograms instantly. 1 lb = 0.453592 kg exactly. Shows the formula and all common weight units.
Enter your values above to see the results.
Tips & Notes
- ✓1 lb = 0.453592 kg exactly. Quick mental estimate: divide pounds by 2.2 (accurate to within 0.2%).
- ✓Luggage limits: most international flights allow 23 kg checked baggage = 50.7 lbs. US domestic flights often allow 50 lbs = 22.68 kg.
- ✓Body weight: 150 lbs = 68.04 kg. 200 lbs = 90.72 kg. 220 lbs ≈ 100 kg — a useful reference.
- ✓Gym equipment: US plates are in lbs (45 lb = 20.41 kg), while international and Olympic equipment uses kg plates (20 kg = 44.09 lbs).
Common Mistakes
- ✗Dividing by 2 instead of 2.2046 — a 10% error. 100 lbs ÷ 2 = 50 kg, but the correct answer is 45.36 kg.
- ✗Confusing pounds (lb) with pounds-force (lbf) — lbf is a unit of force, not mass. In everyday context, lb means mass.
- ✗Using 0.45 instead of 0.453592 — a 0.79% error. Over 200 lbs, this underestimates by 1.58 kg.
- ✗Forgetting that stone is used in the UK — a person weighing 11 stone 4 lbs = 158 lbs = 71.67 kg.
Pounds to Kilograms Overview
What This Calculator Does
Converts pounds to kilograms using the exact internationally defined factor: 1 pound = 0.45359237 kg. This value is exact — defined by the 1959 International Yard and Pound Agreement.
The Formula
kg = lbs × 0.453592
Quick approximation: kg ≈ lbs ÷ 2.2046 (same result, different form)
The Definition of the Pound
The avoirdupois pound — used for body weight, food, and general commerce — has been defined since 1959 as exactly 0.45359237 kilograms. Before this international standardization, the US pound and UK pound differed by a tiny amount, causing issues in trade and science.
There are other types of pounds (troy pound = 373.24 g, used for precious metals; apothecary pound) but in everyday contexts, pound always means the avoirdupois pound.
Common Reference Points
| Pounds | Kilograms | Context | |--------|-----------|---------| | 1 lb | 0.454 kg | Definition | | 22 lbs | 9.979 kg | Typical carry-on weight limit | | 50 lbs | 22.68 kg | US airline checked baggage limit | | 100 lbs | 45.36 kg | Common fitness reference | | 150 lbs | 68.04 kg | Average US body weight reference | | 200 lbs | 90.72 kg | Common heavy reference |
Where Pounds Are Used
Body weight: The US primarily uses pounds for body weight. Medical records, fitness apps, and health guidelines in the US express weight in lbs. Most of the world uses kg.
Food and cooking: US recipes use ounces and pounds. International recipes use grams and kilograms. A 2-pound roast = 907 g ≈ 0.9 kg.
Shipping and luggage: Airline baggage limits are expressed in both pounds and kilograms depending on the carrier and route. Cargo weight is often in pounds in the US.
Fitness: US gym equipment uses pound-based plates. Olympic and international weightlifting uses kilograms. A 45 lb plate = 20.41 kg.
The Mental Math Shortcut
To convert pounds to kg in your head: divide by 2.2. This uses the approximation 1 kg = 2.2 lbs (actual: 2.20462 lbs), introducing a 0.2% error — negligible for everyday use.
Example: 175 lbs ÷ 2.2 = 79.5 kg (exact: 79.38 kg). The 0.12 kg difference is imperceptible in most contexts.