This one-rep max calculator estimates your single maximum lift from a weight you can lift for several reps, using established formulas.
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One-Rep Max Calculator
Estimate one-rep max with Epley and Brzycki formulas.
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About this calculator
Formula notes
Epley: 1RM = w × (1 + reps/30); Brzycki: 1RM = w × 36 / (37 − reps). The page averages both for a balanced estimate.
Worked examples
- Example: 100 kg × 5 reps gives Epley ≈ 116.7 kg and Brzycki ≈ 112.5 kg, averaging ≈ 114.6 kg.
- Lifting 80 kg for 8 repetitions gives an Epley estimate of about 101.3 kg and a Brzycki estimate near 99.3 kg, showing formula spread.
How to use it
- Enter the weight you lifted.
- Enter clean reps performed (stop before failure).
- Read the Epley, Brzycki, and average estimates.
Frequently asked questions
Why do the formulas disagree slightly?
They fit different lifter datasets; the average smooths out individual bias.
Are estimates accurate beyond 10 reps?
Accuracy drops with high reps; use sets of 3–6 reps for the best estimate.
Limits and interpretation
- Prediction error grows when the set is far from failure, technique changes, or repetitions are very high.
- An estimated maximum is not an instruction to attempt that load and does not account for pain, fatigue, equipment, or supervision.