How 1RM Is Calculated
Your one-rep max (1RM) is the maximum weight you can lift for a single repetition. Rather than testing this directly (which can be risky), you can estimate it from submaximal sets.
Formulas
Epley: 1RM = Weight × (1 + Reps / 30)
Brzycki: 1RM = Weight × 36 / (37 − Reps)
Lander: 1RM = 100 × Weight / (101.3 − 2.67123 × Reps)
Lombardi: 1RM = Weight × Reps^0.10
Using Percentages for Training
- 90-100% 1RM (1-3 reps): Maximum strength / neural adaptations
- 75-85% 1RM (5-8 reps): Strength and some hypertrophy
- 65-75% 1RM (8-12 reps): Hypertrophy (muscle building)
- 50-65% 1RM (12-20 reps): Muscular endurance
Frequently Asked Questions
How accurate are 1RM calculators? Most accurate with 3-10 reps. Above 10 reps, accuracy decreases. The Epley and Brzycki formulas are most widely used.
Should I test my actual 1RM? Only if experienced and with a spotter. Estimated 1RM from a 3-5 rep set is safer and nearly as accurate.