How to Use the 1RM Calculator
Your one-rep max (1RM) is the heaviest weight you can lift for a single rep. Actually testing that limit carries real injury risk, so lifters typically estimate it from a lighter weight lifted for multiple reps. This calculator applies the Epley formula, which works for bench press, squat, deadlift, and most other barbell lifts, to estimate your 1RM from the weight and reps you enter.
For example, lifting 135 lb for 8 reps estimates a 1RM of roughly 171 lb. The more reps you perform, the less accurate the estimate tends to be relative to your true max, so calculating from a recent set of 3-8 reps generally gives the most reliable number. The RM conversion table shown with your result lets you read off training weights for specific rep targets, like 5RM or 8RM, which is handy when following a percentage-based program.
Keep in mind this is a statistical estimate, not a guarantee — your actual max depends on your strength curve, technique, and how you're feeling that day. Before attempting a heavy single based on this number, warm up thoroughly and use a spotter, especially for lifts like the bench press with no safety bars.
Frequently Asked Questions
Enter a weight you can lift for multiple reps, and the Epley formula (weight x (1 + reps / 30)) estimates your one-rep max.
Accuracy drops once reps go above 10. For the best estimate, use a recent set of 3-8 reps.