One Rep Max Calculator
Enter your values below and click Calculate for instant results.
Estimate your one rep max from any working set. Includes training percentage chart for all major strength and hypertrophy ranges.
Enter your values below and click Calculate for instant results.
Your one rep max (1RM) is the maximum weight you can lift for exactly one complete repetition of an exercise with good form. It is the foundational measurement in strength training for programming workouts at specific percentages of maximum capacity. You do not need to actually attempt a true 1RM to use this calculator -- you can estimate it from a submaximal set.
Attempting a true 1RM carries injury risk, especially for beginners and intermediate lifters. Estimating from a set of 3 to 8 reps at high effort is safer and nearly as accurate for programming purposes. The formulas become less reliable above 10 to 12 reps.
This calculator averages three established formulas: the Epley formula, the Brzycki formula, and the Lander formula. Each takes your working weight and rep count and extrapolates backward to a theoretical maximum single effort. No single formula is universally most accurate, so averaging the three provides a more reliable estimate across different lifters and movement patterns.
Most strength programs prescribe work at specific percentages of your 1RM. Heavy strength work typically uses 85 to 95% of 1RM for 1 to 5 reps. Hypertrophy-focused training uses 65 to 80% for 6 to 12 reps. Muscular endurance work drops to 50 to 65% for 15 or more reps. The percentage chart in this calculator gives you the working weight for any of these ranges based on your estimated max.