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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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.
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))Work at 80-95% of 1RM for sets of 1-5 to build maximal strength.
Use 65-80% of 1RM for sets of 6-12 to maximize muscle growth.
Train at 50-65% of 1RM for 15+ reps to build muscular endurance.
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.
Different formulas were developed from various populations and exercises. We show multiple formulas so you can see the range. Brzycki and Epley are most commonly used and generally agree within 5%.
Only with proper spotters, equipment, and experience. For most training purposes, working at percentages of estimated 1RM is safer and equally effective. True 1RM testing is typically reserved for competition.
Every 4-8 weeks, or whenever you complete a training cycle. As you get stronger, your estimated 1RM should increase. Use rep PRs to track progress between calculations.