One Rep Max Calculator
Free 1RM calculator to estimate your one rep max for any lift using Brzycki, Epley, Lander, and other proven strength training formulas.
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Calculate Your One Rep Max Safely
Know your true strength without risking injury. This calculator estimates your one rep maximum (1RM) based on weight and reps performed, using multiple validated formulas. Use your 1RM to plan training programs and track progress.
What is One Rep Max (1RM)?
Your 1RM is the maximum weight you can lift for a single repetition with proper form. It's the gold standard for measuring strength and programming training loads. Rather than testing directly (which risks injury), 1RM is typically estimated from submaximal lifts—lifting a lighter weight for multiple reps.
Brzycki Formula (Most Common)
1RM = Weight × (36 / (37 - Reps))How to Use This Calculator
Using Your 1RM
Strength Training
Work at 80-95% of 1RM for sets of 1-5 to build maximal strength.
Hypertrophy Training
Use 65-80% of 1RM for sets of 6-12 to maximize muscle growth.
Endurance Training
Train at 50-65% of 1RM for 15+ reps to build muscular endurance.
Frequently Asked Questions
Estimates are most accurate with 1-10 reps. Under 5 reps gives the best accuracy. Above 10 reps, estimates become less reliable. Testing with your 3-5 rep max is ideal.