One Rep Max (1RM) Calculator
Estimate your one-rep max for any lift based on a weight you can do for multiple reps. Uses three validated formulas.
How 1RM Formulas Work
All one-rep max formulas estimate the maximum weight you could lift for a single repetition based on a weight you can lift for multiple reps. The three formulas used here are the most widely validated in sports science research. Epley (1985): 1RM = w x (1 + r/30). Best for higher rep ranges (5-10). Brzycki (1993): 1RM = w x (36 / (37 - r)). Most accurate for lower rep ranges (2-5). Lombardi (1989): 1RM = w x r^0.10. A good middle ground. This calculator averages all three for the best overall estimate. Accuracy is highest when using a set of 3-6 reps. Above 10 reps, all formulas become less reliable.
How to Use Your 1RM
Strength training (1-5 reps): Work at 85-100% of your 1RM. Hypertrophy / muscle building (6-12 reps): Work at 65-85% of your 1RM. Endurance (12-20 reps): Work at 50-65% of your 1RM. Most programs prescribe weights as a percentage of your 1RM. Knowing your estimated max lets you program accurately without actually attempting a true one-rep max, which carries more injury risk.
1RM FAQ
Which formula is most accurate?
Brzycki tends to be most accurate for low reps (2-5). Epley tends to be more accurate for moderate reps (5-10). For high reps (10+), all formulas lose accuracy. Using the average of all three (which this calculator does) gives the most reliable overall estimate.
Should I actually attempt a 1RM?
For most recreational lifters, no. True 1RM attempts carry injury risk, especially on exercises like squats and deadlifts. Estimating from a 3-5 rep set is safer and almost as accurate. Competitive powerlifters and weightlifters do test true 1RMs, but with proper warm-up, spotters, and experience.
How often does my 1RM change?
Beginners can see 1RM increases every 1-2 weeks. Intermediate lifters progress monthly. Advanced lifters may only add a few pounds per year. Retest or re-estimate every 4-8 weeks to keep your training percentages accurate.
What is a good 1RM for bench press?
General strength standards for adult males: beginner (body weight x 0.5-0.75), intermediate (body weight x 1.0-1.25), advanced (body weight x 1.5+). For adult females: beginner (body weight x 0.25-0.5), intermediate (body weight x 0.75-1.0), advanced (body weight x 1.0-1.25). These are rough guidelines and vary by age, training experience, and body composition.