Epley One-Rep Max Calculator
Your one-rep max (1RM) is the most weight you can lift for a single repetition of an exercise. Lifting near a true 1RM carries risk, so it is often estimated from a submaximal set instead. The Epley formula estimates 1RM from the weight lifted and the number of repetitions completed. This tool applies the Epley equation and also estimates the weight for other rep targets. Estimates are approximate and vary by person and exercise.
Epley formula
Estimated 1RM = weight * (1 + reps / 30)
For r reps: weight = 1RM / (1 + r / 30)
Weight can be in any consistent unit (the result uses the same unit). The formula assumes the set is taken close to failure. When reps equals 1, the formula returns the weight lifted unchanged. Higher rep counts increase the estimated 1RM.
Worked example
For 100 lifted for 5 reps: estimated 1RM = 100 * (1 + 5 / 30) = 100 * 1.16667 = 116.67. To find the weight for 10 reps, divide the 1RM by (1 + 10 / 30): 116.67 / 1.33333 = 87.50.
Frequently asked questions
How accurate is the Epley estimate?
Repetition-based 1RM formulas are approximations. They are most accurate at low rep counts (roughly 10 or fewer) and for trained lifters, and they can over- or under-estimate at high reps. Use the figure as a guide, not an exact maximum.
How does Epley differ from Brzycki?
Both estimate 1RM from weight and reps but use different equations, so they give slightly different numbers. Epley tends to estimate a little higher than Brzycki at higher rep counts. Neither is universally correct.
Should I actually attempt a true 1RM?
Attempting a genuine 1RM carries injury risk and should only be done with proper warm-up, technique, and ideally a spotter. Estimating from a submaximal set avoids that risk, which is the point of the formula.
What units does it use?
Any consistent unit. If you enter kilograms, the result is in kilograms; if you enter pounds, it is in pounds. The formula does not depend on the unit.
Sources
- Epley B, repetition-based one-rep-max estimation, summarised at the U.S. National Library of Medicine: PubMed.
- U.S. Department of Health and Human Services: Physical Activity Guidelines for Americans.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. Educational training estimate. See our methodology.