One Rep Max Calculator
Estimate your one-rep max from a submaximal set using the Epley and Brzycki formulas, with a percentage training table.
How it works
Epley: 1RM = w × (1 + reps ÷ 30) · Brzycki: 1RM = w × 36 ÷ (37 − reps)
Both formulas extrapolate a hard submaximal set to a single all-out rep. Epley and Brzycki agree closely through about 10 reps and diverge beyond that, so this calculator averages the two and limits input to the 2–12 range where they are validated. Estimates run within roughly ±5% for trained lifters on big barbell lifts, with more error on isolation moves.
Worked example
200 lb for 5 reps: Epley = 200 × (1 + 5/30) = 233 lb; Brzycki = 200 × 36 ÷ 32 = 225 lb; the average, 229 lb, is the working estimate. 80% of that — about 183 lb — is a typical 8-rep training weight.
Frequently asked questions
Which formula should I trust?
For 2–6 reps they nearly agree; Brzycki drops off faster at higher reps. The average of the two is a sensible middle. Whatever you use, the set must be near-failure — a comfortable 5 says little about your max.
Should beginners test a true 1RM?
Usually not — max singles are a skill of their own and carry the most injury risk before technique is stable. Estimated maxes give beginners everything programming needs.
How do I use the percentage table?
Strength work typically lives at 80–95% for 2–8 reps; hypertrophy at 65–80% for 8–12. If a prescribed percentage feels wrong on the day, adjust — the table is a map, not a contract.
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This calculator is for educational purposes. Double-check important results before acting on them.