1RM Calculator
Estimate your one rep max using 6 proven strength training formulas. Enter the weight you lifted and how many reps you completed.
What is a One Rep Max (1RM)?
Your one rep max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise. It’s one of the most important metrics in strength training, used by powerlifters, bodybuilders, and coaches to design training programs and track progress over time.
Rather than attempting a true maximal lift — which carries injury risk and requires significant recovery — most lifters estimate their 1RM using submaximal sets. If you can bench press 100 kg for 5 reps, mathematical formulas can predict what you’d be able to lift for a single rep.
This calculator uses six well-established formulas (Epley, Brzycki, Lombardi, Mayhew, O’Conner, and Wathan) and averages them for the most reliable estimate. Each formula was developed through research on different populations, so averaging reduces the bias of any single method.
The percentage table helps you plan your training loads. For example, many programs prescribe sets at 70-85% of 1RM for hypertrophy, and 85-95% for strength. With your estimated 1RM, you can hit the right intensity every session.