1 Rep Max (1RM) Calculator

No single formula is universally most accurate — accuracy varies by individual, training background, and exercise. The average of multiple formulas reduces individual formula bias. All formulas become less accurate above 10 reps because technique, endurance, and mental fatigue affect high-rep sets differently than low-rep maximal efforts.

Training percentages of 1RM are used for different adaptations: 85–95% 1RM for maximal strength (1–3 reps), 70–85% for hypertrophy (6–12 reps), 60–70% for strength-endurance (12–20 reps). Programs like 5/3/1 and percentage-based powerlifting programs use 1RM as their training base.

Direct 1RM testing carries injury risk, especially for beginners and those without a spotter. Estimate from rep sets for most training purposes. If you do test directly, warm up thoroughly, use a spotter for upper body lifts, make small weight jumps, and only attempt once you are well-practised with the movement.