One Rep Max Calculator
Best accuracy with 1–10 reps
Estimated 1RM
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The Formulas
Training Percentage Guide
Frequently Asked Questions
Which formula is most accurate?
No formula is perfectly accurate — they are all estimates based on population averages. Epley is the most widely used and tends to be reliable for moderate rep ranges (3–10 reps). All formulas become less accurate above 10 reps. For best accuracy, test with a weight you can lift for 3–5 reps with good form.
Should I actually attempt my calculated 1RM?
Not necessarily, and not without proper preparation. Maximal effort lifts carry injury risk and require adequate warm-up, spotting, and technique. The estimated 1RM is primarily useful for programming training percentages — for example, working at 75% for hypertrophy or 85–90% for strength work.
What percentages are used for different goals?
55–65% is used for muscular endurance (12–20+ reps). 67–85% is the hypertrophy range (6–12 reps). 85–95% builds maximal strength (1–5 reps). 95–100% is used for competition or true max testing. Most strength programs prescribe work in the 70–90% range.
Does 1RM differ between people of the same strength level?
Yes. Some people are naturally better at high-rep efforts (more muscle fiber endurance), others peak at low reps (more fast-twitch dominant). This is why a formula estimate from 10 reps may differ from a formula estimate from 3 reps for the same person — the lower rep test is usually more accurate for predicting true max.