How to Convert Pounds to Kilograms
Mass · Last updated: July 2025
Pounds (lb) and kilograms (kg) measure mass. In everyday US English we say “weight,” but the conversion factor applies to mass units. The international definition uses 1 lb = 0.45359237 kg (often rounded to 0.453592 in calculators).
The formula
Kilograms = pounds × 0.453592
Pounds = kilograms ÷ 0.453592 (or × 2.20462)
Rule of thumb: divide pounds by 2 and subtract 10% for a rough kg estimate (150 lb → ~68 kg actual 68.04).
Quick reference
| From | To |
|---|---|
| 1 lb | 0.454 kg |
| 5 lb | 2.27 kg |
| 10 lb | 4.54 kg |
| 50 lb | 22.68 kg |
| 100 lb | 45.36 kg |
| 154 lb (≈70 kg) | 70 kg |
| 1 kg | 2.205 lb |
Where this conversion shows up
Body weight and fitness
Scales, gym equipment, and international race categories may use kg. Athletes comparing power-to-weight (watts per kg) need consistent units.
Airline baggage
US carriers often allow 50 lb checked bags; international routes may state 23 kg. 50 lb ≈ 22.7 kg—slightly under the limit, but always confirm with your airline.
Cooking and retail
Some imported foods list net weight in kg while US recipes use pounds. Meat counters and produce scales may switch units by store.
Mass vs weight
Scientifically, “weight” depends on gravity; “mass” does not. For Earth-surface practical conversions (people, packages, food), lb↔kg as mass units is standard. Do not use lb↔kg for force (newtons) without a different formula.
Common mistakes
- Confusing ounces (oz) of mass with fluid ounces (fl oz) of volume.
- Using 0.45 exactly in medical or legal contexts where full precision is required.
- Mixing stone (UK body weight) without converting to lb first.
References
Enter 150 lb or 68 kg on the tounits.com converter.