One-Rep Max (1RM) Calculator
The one-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. This calculator estimates your 1RM using proven formulas so you can plan your training without the risk of actually attempting a max lift.
The Epley formula (1RM = weight x (1 + reps/30)) and the Brzycki formula (1RM = weight x 36/(37 - reps)) are the two most widely used methods for estimating one-rep max. Both are most accurate when using sets of 10 or fewer repetitions. For higher rep ranges, accuracy decreases but the estimates remain useful for programming purposes.
Knowing your 1RM allows you to calculate training percentages for different goals. Strength training typically uses 80-95% of 1RM for 1-5 reps, hypertrophy training uses 65-80% for 6-12 reps, and muscular endurance training uses 50-65% for 15+ reps. These percentages provide a framework for progressive overload.
For safety, it is generally recommended to estimate your 1RM using submaximal loads rather than actually attempting a true one-rep max, especially for exercises like squats, deadlifts, and bench press. Always use a spotter or safety equipment when training near your maximal capacity.