One-Rep Max Calculator
Enter the weight you lifted and how many reps you completed to estimate your one-rep max.
Uses the Epley formula: 1RM = weight × (1 + reps/30).
How one-rep max is estimated
The Epley formula estimates your one-rep max as weight × (1 + reps/30). This is based on the observed relationship between the number of reps you can complete at a given weight and your true single-rep maximum, without needing to actually attempt a risky maximal single lift.
This estimate becomes less accurate at higher rep counts (generally above 10-12), since the relationship between reps and strength becomes less linear — for the most reliable estimate, use a set of 2-8 reps performed close to failure.
Frequently asked questions
Why estimate 1RM instead of just testing it directly?
Testing a true one-rep max carries higher injury risk, especially for less experienced lifters, and requires significant warm-up and recovery time. Estimating from a submaximal set (like 5 reps) is safer and still gives a useful benchmark for programming training weights.
Is the Epley formula the only one-rep max formula?
No — other common formulas include the Brzycki formula and the Lander formula, which use slightly different equations and can give modestly different estimates, especially at higher rep counts. No formula is perfectly accurate for everyone since individual rep-to-strength relationships vary.
How should I use my estimated 1RM?
Estimated 1RM is commonly used to calculate training percentages — for example, programming a set at 80% of your estimated 1RM. Since it's an estimate, treat the resulting training weights as a starting point and adjust based on how the lift actually feels.