1RM Calculator
Find your one rep max
Estimate your 1RM from any weight and rep count - without lifting to failure. Three formulas, one precise answer.
What is a 1RM?
1RM (one rep max) is the maximum weight you can lift for exactly one complete repetition with correct form. It is the gold standard for measuring absolute strength in the gym.
Your 1RM is the foundation of all percentage-based strength programs. Whether you follow a 5/3/1, linear progression, or a percentage-based powerlifting program - everything is calculated from your 1RM.
The three formulas
The average of all three is the most reliable estimate. For 2-6 reps all three formulas converge to nearly the same result. Above 10 reps they diverge, so stick to 2-8 reps for the best estimates.
How to use your 1RM in training
Strength development
Work at 85-95% of your 1RM for 1-5 reps. This range develops maximum strength and improves the neural adaptations that make you stronger.
Hypertrophy (muscle growth)
Work at 67-85% of your 1RM for 6-12 reps. This range maximizes muscle growth while still building strength.
Muscular endurance
Work at 50-67% of your 1RM for 15+ reps. Lower intensity, higher volume - builds work capacity.
Your AI coach knows your 1RM on every exercise
Gainfully tracks every set and suggests the optimal weight for next time - automatically.
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Frequently asked questions
Which formula is most accurate?
Epley is most widely used and accurate for general use. Brzycki is slightly better for low reps (1-6). Landers performs well for moderate reps (5-10). The average of all three is the safest bet.
Is it safe to test my actual 1RM?
Yes, with proper technique and warm-up. But for most lifters, estimating from submaximal weights (3-8 reps) is safer and reduces injury risk - especially for the squat and deadlift.
How often should I test my 1RM?
Your estimated 1RM updates every time you log a set in Gainfully. An actual max test is typically done every 8-16 weeks, at the end of a training block.