One-rep max calculator
Estimate a maximum from a set you have actually done, without the risk of testing a true single. The rep chart below it gives you the load to use for every other rep range.
One Rep Max Calculator
Estimate a one-rep max with Epley, 1RM = weight × (1 + reps / 30), or Brzycki, 1RM = weight × 36 / (37 − reps). Five reps at 100 kg gives roughly a 117 kg maximum by Epley and 112.5 kg by Brzycki. Accuracy is best between one and five reps and degrades noticeably past ten.
Epley 116.7 kg · Brzycki 112.5 kg
Method notes (3)
- Estimated 1RM — an extrapolation from a submaximal set, not a tested max. Most accurate at 1–5 reps; it drifts high past ~10 reps and past ~12 it's a rough guide only.
- Epley (116.7 kg) and Brzycki (112.5 kg) are shown side by side; they agree closely at low reps and diverge as reps climb.
- The rep table uses the standard Brzycki %-of-1RM chart — treat the loads as starting points and adjust to how the bar actually moves.
Metric or imperial · runs the same code as the app · nothing is sent anywhere
How it works
Epley: 1RM = w × (1 + reps / 30). Brzycki: 1RM = w × 36 / (37 − reps). They agree closely at low rep counts and diverge as reps climb, with Epley reading higher.
The rep chart uses the classic Brzycki percentage table, (37 − r) / 36, which reads exactly 100% at one rep: roughly 97% for a double, 94% for a triple, 89% for five, 81% for eight and 75% for ten.
Accuracy is best between one and five reps. Past about ten, fatigue, technique breakdown and rep cadence matter more than the arithmetic, so a 15-rep set makes a poor predictor.
Common questions
Which 1RM formula is most accurate?
Neither dominates. Epley tends to read slightly high at moderate reps and Brzycki slightly low; averaging them is a reasonable hedge. The bigger factor is how close your set was to failure.
Should I test a real one-rep max instead?
Rarely worth it outside competition. A true single is fatiguing, carries more injury risk and needs a spotter. A hard set of three to five gives you a usable estimate at a fraction of the cost.
Why does my estimate differ between sessions?
Because an estimate assumes the set was taken near failure. Sleep, food, stress and how many reps you left in reserve all move it. Track the trend rather than any single figure.
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