One Rep Max Calculator

The Epley formula estimates your true one-rep max (1RM) from a set taken with lighter weight for multiple reps: weight × (1 + reps/30). It's one of the most widely used estimation formulas in strength training because it only needs two numbers — the weight used and the reps completed — and stays reasonably accurate across the rep ranges lifters train in most.

The relationship between reps and %1RM is roughly linear at low reps but flattens out as reps climb, so formulas built on that linear assumption start to overstate the true max past about 10–12 reps. A 20-rep set fed into the Epley formula will typically produce a number well above what you could actually lift once.

Each row converts your estimated 1RM into the weight you should load for a given rep target. If your program calls for a set of 8, use the 8-rep row — roughly 80% of your estimated max — rather than guessing a weight and hoping the reps work out.

No. A true 1RM test means loading a bar until you fail, which carries real injury risk without a spotter or safety bars and takes a dedicated session to do properly. This estimate is meant for programming your training weights day to day — if you need a certified max for a meet or a coaching benchmark, that still calls for a supervised test.

Estimation formulas like Epley were developed on and hold up best for compound barbell lifts — squat, bench press, deadlift, overhead press — where technique stays consistent as fatigue builds across the set. They are less reliable for isolation or machine exercises, where the last few reps of a set often break down differently.