Epley: 1RM = w × (1 + reps ÷ 30). Brzycki: 1RM = w × 36 ÷ (37 − reps). Lombardi: 1RM = w × reps^0.10. The three are averaged, and the table applies each percentage to that average.
Epley (1985); Brzycki (1993); Lombardi (1989).
Most accurate at 5 reps or fewer. Past ~10 reps the estimates drift upward as muscular endurance, not maximal strength, becomes the limiting factor.
Untrained beginners (rep quality is inconsistent) and rehab or medical contexts — do not test or estimate maximal loads without appropriate supervision.
Frequently asked questions
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition of an exercise. It's the standard benchmark for strength and the basis for setting training percentages.
From a set you've already done. Enter the weight and how many reps you managed, and three validated formulas — Epley, Brzycki, and Lombardi — estimate the single-rep weight. We average them for a balanced figure.
Most accurate when your set was 5 reps or fewer. As reps climb past about 10, endurance rather than pure strength starts to limit the set, so every formula drifts and tends to over-estimate.
Each models the strength-to-endurance curve slightly differently. Brzycki tends to read a touch lower at higher reps, Epley and Lombardi a touch higher. The average smooths out those differences.
It shows the weight for each percentage of your 1RM, with roughly how many reps that load allows. Programs often prescribe work like '5×5 at 80%' — read that row straight off the table.
Rarely, and only when well warmed up, experienced, and ideally with a spotter. For most people the estimate from a hard set of 3–5 reps is safer and precise enough to program from.