One Rep Max Calculator

Estimating One Rep Max Safely

One Rep Max (1RM) is the maximum weight you can lift for one repetition with proper form. Testing true 1RM can be risky and cause injury. This calculator estimates 1RM based on submaximal weights, allowing safer training. Two popular formulas exist: Epley formula and Brzycki formula. Epley tends to be more accurate for lower reps (1-5), while Brzycki is accurate for higher reps (6-10). Use the average of both formulas for best results. Important: estimates become less accurate above 10 reps. True 1RM testing should only be done under expert supervision with proper warm-up and form checks. Use estimated 1RM to calculate training weights: 80% of 1RM for strength training, 65-75% for hypertrophy, 50-60% for endurance. Progress systematically—add 2.5kg for upper body, 5kg for lower body when you can complete all reps with good form.