1RM Calculator
Estimate your one-rep max from a set of any rep count (Epley, Brzycki and Lombardi averaged) and get a full percentage table for programming your working sets.
Use a genuinely hard set — one or two reps in reserve at most. A comfortable set will under-read badly.
How this is worked out
Three standard estimators are averaged: Epley (w × (1 + r/30)), Brzycki (w × 36/(37 − r)) and Lombardi (w × r0.1). They disagree by a few percent and each behaves best in a different rep range, so the spread is shown rather than one being presented as the answer.
Accuracy depends entirely on the set being close to failure. From sets of 1–5 the estimate is good; above about 12 reps it drifts optimistic, because endurance rather than strength is what ended the set.
Working weights are rounded to the nearest 2.5 — the smallest plate pair most gyms have.
Information only — not medical advice. These are estimates from population-level formulas, not a substitute for professional assessment. See our full disclaimer.