Free tool
Estimate your one-rep max from your lifted weight and number of reps. Free tool, no sign-up required.
Testing your true 1RM , the maximum load you can lift once , is risky without specific preparation. Poor execution can cause injury, and the result depends heavily on daily fatigue. Estimation formulas like Epley, Brzycki, and Lombardi use a submaximal set (what you lift for 3-10 reps) to estimate your theoretical maximum with ±5% accuracy. It's safer, more reproducible, and precise enough to program your training.
Epley (1985) is the most used in strength training, reliable between 2-10 reps. Brzycki (1993) gives slightly more conservative results , the powerlifter favorite. Lombardi (1989) uses a logarithmic curve, particularly accurate on heavy loads (1-5 reps). The average of all three gives the most robust estimate for most lifters.
Your 1RM serves as a reference to program your loads by percentage. For hypertrophy, work between 65-80% of your 1RM for 8-12 reps. For strength, aim for 80-95% for 3-6 reps. For muscular endurance, stay at 50-65% for 15+ reps. Recalculate your 1RM every 4-6 weeks to track your progress.
Your estimated one-rep max
Valid rep range: 1 to 12. Formulas lose accuracy beyond 10 reps.
The 1RM calculator is an essential tool for planning your strength cycles. It lets you determine your working loads without testing your actual maximum, reducing injury risk while giving you a reliable basis for programming your percentage-based sessions.
The one-rep max (1RM) is the heaviest load you can lift for a single repetition with proper technique. Instead of testing it directly (risky without preparation), these formulas estimate it from a submaximal set.
1RM = Weight x (1 + Reps / 30). The most used in strength training. Very reliable between 2 and 10 reps.
1RM = Weight x (36 / (37 - Reps)). Slightly more conservative. Popular in powerlifting circles.
1RM = Weight x Reps^0.10. Logarithmic formula, accurate on heavy loads (1-5 reps).
This calculator gives you a one-time estimate. Atlo records every session, tracks your strength progression, and automatically adjusts your working loads. Join the waitlist.
lockNo spam. We'll email you at launch.