Pounds to kilograms, without the guesswork
The exact lb ↔ kg factor, the mental math that gets you close in a second, and why gym plates never line up between the two systems.
1 min read
Written & reviewed by Ricardo Tapia·Last updated
One pound is exactly 0.45359237 kg — that's a definition (the 1959
international agreement), not a measurement. So kg = lb × 0.45359237 and
lb = kg ÷ 0.45359237 are always right; the only error comes from rounding
the answer.
For the gym floor you rarely need all eight decimals. Divide pounds by 2.2 to get kilos, multiply kilos by 2.2 to get pounds — under 1% off, which is well inside the noise of a warm-up set.
Even quicker for lb → kg: halve the number, then take off 10%. 200 lb → 100 → 90 kg (true answer 90.7).
Why plates never match
Plates aren't converted, they're manufactured in whole units of each system — so a "same" bar weighs slightly different amounts in a pound gym and a kilo gym.
- A 45 lb plate is 20.41 kg; a 20 kg plate is 44.09 lb.
- A competition Olympic bar is 20 kg = 44.09 lb, not 45 — many US gyms use a 45 lb (20.41 kg) bar instead.
- 225 lb is 102.06 kg, and 100 kg is 220.46 lb. The "two plates" milestone is not the same lift on both sides of the Atlantic.
If you're logging a lift or reporting bodyweight, use the exact number. If you're picking a warm-up, round to whatever your rack actually has.
Try it
Convert any amount in the lb ↔ kg converter, then use the plate calculator to load the bar.
Educational content only. Not medical advice — consult a professional for your situation.