Gym math
45 lb vs 20 kg plates
They look the same on the bar, but they aren't the same weight: a 20 kg plate is 44.09 lb, and a 45 lb plate is 20.41 kg. The gap is 0.91 lb (0.41 kg) per plate.
M. Imtinan Farooq · Updated · 2 min
The exact numbers
One kilogram is 2.20462 pounds, so:
- 20 kg = 44.09 lb
- 45 lb = 20.41 kg
Kilo plates in pounds
| Kilo plate | In pounds |
|---|---|
| 25 kg | 55.12 lb |
| 20 kg | 44.09 lb |
| 15 kg | 33.07 lb |
| 10 kg | 22.05 lb |
| 5 kg | 11.02 lb |
| 2.5 kg | 5.51 lb |
| 1.25 kg | 2.76 lb |
Pound plates in kilos
| Pound plate | In kilos |
|---|---|
| 55 lb | 24.95 kg |
| 45 lb | 20.41 kg |
| 35 lb | 15.88 kg |
| 25 lb | 11.34 kg |
| 10 lb | 4.54 kg |
| 5 lb | 2.27 kg |
| 2.5 lb | 1.13 kg |
How much the difference adds up
The gap per plate is small, but it grows with every plate on the bar. Three plates a side:
- Pound gym: 45 lb bar + six 45s = 315 lb (142.9 kg)
- Kilo gym: 20 kg bar + six 20s = 140 kg (308.6 lb)
That's about 6.4 lb (2.9 kg) apart for what both lifters call "three plates". It matters when you compare numbers between gyms, convert a meet total, or chase a PR in one system after training in the other.
Mixing kilo and pound plates
Putting a 45 lb plate on one side and a 20 kg plate on the other leaves one side 0.91 lb heavier. You won't feel that on a single pair, but it makes your logged total wrong, and the error grows with every mixed pair. If your gym has both, keep each bar in one system, and log in the unit of the plates you used.
The plate calculator works in either unit, and the weight on bar calculator shows the conversion under every total.
Do the math for your own bar
Questions
Is 20 kg the same as 45 lb?
No. 20 kg is 44.09 lb, and 45 lb is 20.41 kg. They're close enough to swap for a single training set, but not the same.
Is 100 kg the same as 225 lb?
No. 100 kg is 220.5 lb. Two 20 kg plates a side on a 20 kg bar is 100 kg, while two 45s on a 45 lb bar is 225 lb.
Which is heavier, a 45 lb plate or a 20 kg plate?
The 45 lb plate, by 0.91 lb (0.41 kg).