One Rep Max Calculator

Why four formulas and what separates them

Epley adds a fixed fraction per rep: w × (1 + reps / 30). Brzycki divides instead: w × 36 / (37 − reps). They agree almost exactly at ten reps and diverge either side — Brzycki reads higher at low reps, Epley higher at high reps. Lombardi uses a power curve and O'Conner a simple linear bump. Below about six reps all four land within a couple of per cent of each other, which is why the spread shown above is a useful warning light.

Reps in reserve changes everything

Every one of these formulas assumes the set ended because another rep was impossible. Stop two reps short and the estimate is low by roughly the value of those two reps — often five to seven per cent. This page adjusts for reserve reps by adding them back before estimating, which is better than ignoring the issue but still an approximation of how close you truly were.

The estimate is lift-specific

A squat and a bench press do not behave the same way across rep ranges. Lifts using large muscle groups with a long range of motion, like the squat and deadlift, tend to allow more reps at a given percentage than the bench press does. Programme from percentages by all means, but expect to recalibrate per lift rather than trusting one table everywhere.

Testing a true max carries real risk

A genuine one-rep attempt means maximal load with fatigue and often poor bar speed — the conditions where technique breaks down. For most people an estimate from a set of three to five is accurate enough to programme with and far safer. If you do test, warm up thoroughly, use a spotter or safety pins, and do not test when tired or unwell.

Frequently Asked Questions