How to use this calculator
- Enter your own values in the labeled fields. Check the units and assumptions before comparing results. Only the fields needed for your selected calculation mode are shown.
- Your answer updates automatically. Review the calculation steps to see exactly how it was calculated.
- Copy, share, save, or download your result. Saved inputs stay on this device.
How the calculation works
Enter a completed near-maximal set, with consistent technique, rather than a light warm-up. Prediction accuracy changes across exercises, experience and repetition counts, so this tool limits sets to ten repetitions and shows both equations. A single repetition is treated as the weight itself. An estimate is not an instruction to attempt a heavier lift.
A worked example
For 80 kg lifted 5 times, Epley gives 80 × (1 + 5/30) = 93.3333 kg; Brzycki gives 80 × 36/32 = 90 kg.
Reading your result
Use the main result together with its units and supporting figures. Display values are rounded; calculations keep their underlying precision. A change in inputs or assumptions can change the answer. Compare the step-by-step working with your intended use before relying on an estimate.
Frequently asked questions
Why do equations disagree?
They are different prediction models, not exact physical identities.
Can I use 20 repetitions?
No. This implementation accepts 1–10 repetitions to limit extrapolation.
Sources & methodology
Research: muscular endurance and one-repetition strength prediction ↗
Formula review: October 24, 2026. Read our methodology.