One-rep max calculator
Your estimated one-rep max is the average of seven formulas. Example: 100 kg for 5 reps gives 115.5 kg (range 112.5–119.0).
Seven formulas, one set
| Formula (100 kg × 5) | 1RM |
|---|---|
| Epley | 116.7 kg |
| Brzycki | 112.5 kg |
| Lombardi | 117.5 kg |
| Mayhew | 119.0 kg |
| O’Conner | 112.5 kg |
| Wathan | 116.6 kg |
| Lander | 113.7 kg |
Average 115.5 kg; spread 112.5–119.0 kg. This is why one-rep max calculators disagree.
Reps as % of your max (Epley)
| Reps | % of 1RM |
|---|---|
| 1 | 100% |
| 2 | 94% |
| 3 | 91% |
| 5 | 86% |
| 8 | 79% |
| 10 | 75% |
Which formula fits?
Between about 2 and 10 reps the seven formulas stay within a few percent of each other; we show their average and the spread. Above 10 reps they drift apart, so treat the result as a rough guide. A single (1 rep) is your max, so every formula returns the weight.
Formulas as commonly cited: Epley (1985), Brzycki (1993), Lombardi (1989), Mayhew et al. (1992), O’Conner et al. (1989), Wathan (1994), Lander (1985).
Questions
Why do one-rep max calculators give different answers?
They use different published formulas. For 100 kg × 5 the seven common ones range from 112.5 to 119.0 kg.
Can I use pounds?
Yes. Press lb; the formulas work the same in either unit.
Is anything I type sent to you?
No. The calculator runs in your browser and nothing you enter leaves your device.