One Rep Max Calculator
Enter a weight you can lift for a few clean reps — get your estimated 1RM and the training percentages programmers actually use.
The last rep should have been hard but achievable without breaking form. If you ground it out or had a spotter help, the estimate runs high.
How the math works
The Epley formula is the most widely used estimator: it assumes each additional rep you complete represents about 1/30 more of your maximum. Five reps at 100 kg implies a ~117 kg single. Estimates from sets of 1–6 reps are quite accurate; beyond 10 reps they drift optimistic because muscular endurance takes over as the limiter. Whichever formula you use, treat the number as a planning anchor that gets corrected every few weeks by real training.
Training percentages
The reason a 1RM matters is percentage-based programming: 75–85% of 1RM for 3–6 reps builds maximal strength; 65–75% for 8–12 reps favors muscle growth; anything above 90% is peeking — occasional singles that teach your nervous system to be strong without much building. New lifters don't need true max testing at all; sub-max sets like this one are exactly how the estimate should be made.
FAQ
- Should I ever actually test my 1RM?
- Only with several years of training, a spotter, and warm-up protocol — and never on a max-out whim. For everyone else, this calculator plus rep records is enough.
- Does it work for all lifts?
- Best on squats, bench, deadlift and presses. It's less reliable on very light accessory movements and single-joint exercises.
- Why do my deadlift and squat estimates differ so much?
- Body proportions and leverages differ — most people have a notably stronger deadlift or squat relative to bench. Compare each lift to its own history, not across lifts.
This tool provides general information only and is not medical or training advice. Lift within your ability, use a spotter for heavy barbell work, and consult a professional for personal programming.