Officially, 1 lb = 0.453592 kg. Here’s a memory trick:
Quick estimate
Divide pounds by 2, then subtract 10% of that half.
Example: 180 lb → half is 90 → 10% of 90 is 9 → 90 − 9 = 81 kg (exact is 81.65 kg).
Reverse (kg to lb)
Double the kg, then add 10%.
Example: 70 kg → double is 140 → add 14 → 154 lb (exact is 154.32 lb).
Need precise results?
Use our Weight Converter (lbs, kg, stones): /weight-converter
Common checkpoints
10 lb ≈ 4.5 kg
50 lb ≈ 22.7 kg
100 lb ≈ 45.4 kg