1RM calculator
Estimate your one-rep max without turning every training day into a max-out day.
Estimate your one-rep max
Best for hard sets where the final reps looked like the same exercise you started with.
Useful range. Still, the set needs to be close to failure for the estimate to mean much.
The useful number, with the asterisks left in
What this number means
An estimated one-rep max is a planning number. It helps you choose training loads, compare progress, and avoid testing a true max too often.
The default estimate uses the Epley equation because it behaves sensibly for common gym rep ranges. The Brzycki estimate is shown beside it so you can see whether the formulas broadly agree.
What it does not know
A formula cannot see your technique, range of motion, bar speed, fatigue, exercise selection, or whether the final rep was actually near failure.
Higher-rep sets create wider estimates. Once you enter more than 12 reps, treat the output as a rough training anchor rather than a max-strength claim.
How to use it
Use the estimate to set training percentages, compare blocks, or choose conservative attempts. If the set was not close to failure, the estimate will usually undershoot your true max.
For big lifts, a range is often more honest than one magic number. If Epley and Brzycki disagree, start your programming from the lower side.
When not to trust it
Do not treat an estimated max from a sloppy set, partial reps, a new exercise, or a high-rep burnout as a precise strength test.
If you are returning from injury or learning a lift, use technique quality and coaching judgment before the calculator output.
Caveats
- Most useful for hard sets of roughly 2 to 12 reps.
- Exercise skill, body size, and training history can shift the rep-to-percentage relationship.
- Machine lifts and free-weight lifts may not transfer cleanly.
Examples
- 100 kg for 5 reps estimates roughly 117 kg by Epley.
- 225 lb for 8 reps estimates roughly 285 lb by Epley.
Where the method comes from
- Hoeger et al. Relationship Between Repetitions and Selected Percentages of One Repetition Maximum. Journal of Strength and Conditioning Research. 1987.
- Shimano et al. Relationship between the number of repetitions and selected percentages of one repetition maximum in free weight exercises. Journal of Strength and Conditioning Research. 2006.
- ACSM position stand: Progression models in resistance training for healthy adults. Medicine and Science in Sports and Exercise. 2009.