One-rep max calculator
Estimate the heaviest weight you could lift once from a set you have already done, without testing a true maximum.
Your estimated one-rep max
Enter the weight and reps from a recent hard set, then estimate.
How the formulas work
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Both formulas turn a submaximal set into an estimated single-rep maximum. They are most reliable for sets of about 10 reps or fewer, so the calculator accepts 1 to 10. We show both and their average.
Worked example
You bench-press 80 kg for 5 clean reps. Epley: 80 × (1 + 5 ÷ 30) = 93.3 kg. Brzycki: 80 × 36 ÷ 32 = 90.0 kg. The average is 91.7 kg. At 80 percent of that average the bar would be 73.3 kg.
Limits and safety
- The result is an estimate. It differs by exercise, technique, fatigue and individual, and can be several percent off.
- Use a set taken close to failure with good form. A set that stopped far from failure will underestimate.
- Do not test a true one-rep max alone or without a spotter or safety bars, and avoid it as a beginner. Ask a qualified coach.
- The percentage table is arithmetic, not a training programme.
Who this tool is for
This tool is for healthy adults aged 20 and older. It is not for use during pregnancy or breastfeeding, and it does not diagnose any condition, suggest medicine doses, set weight-loss targets or write personal meal plans. If you have a medical condition, or a result worries you, speak to a doctor or registered dietitian.
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Sources
- Epley B (1985). Poundage chart. Boyd Epley Workout. University of Nebraska
- Brzycki M (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance 64(1):88–90
See the editorial methodology for how we check sources.