One Rep Max Calculator
Estimate your one-rep max (1RM) for a lift from the weight and reps you completed, using the Epley and Brzycki formulas.
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Your result
116.7 kg
One rep max (Epley)
AI explanation
Formula
Epley: 1RM = weight × (1 + reps/30). Brzycki: 1RM = weight × 36 / (37 − reps)Worked example
100kg for 5 reps
| Field | Value |
|---|---|
| Weight lifted | 100 |
| Reps completed | 5 |
| One rep max (Epley) | 116.7 |
| One rep max (Brzycki) | 112.5 |
Assumptions
- Both formulas are estimates that lose accuracy above roughly 10-12 reps — for a true max, a low-rep test (1-3 reps) is more reliable than an estimate.
- Informational only — always use proper form and, for heavy attempts, a spotter.
Frequently asked questions
What is a one-rep max (1RM)?
The maximum weight you can lift for a single repetition with good form — used to gauge strength and to set percentage-based training loads.
Why do the Epley and Brzycki formulas give different results?
They're both empirical fits to rep-max data using slightly different assumptions, so they diverge somewhat, especially at higher rep counts. Neither is definitively "correct" — they both estimate the same underlying quantity.
Should I actually attempt my estimated 1RM?
Not without appropriate warm-up, spotting, and experience — these estimates are a planning tool, not a substitute for a properly supervised max-effort test.
Related calculators
Sources
- Poundage chart — Boyd Epley (National Strength and Conditioning Association). Effective 01-01-1985, reviewed 13-09-2026.
This calculator provides a general estimate only and does not constitute personalized fitness or medical advice. Consult a qualified trainer before attempting a new one-rep max.
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