One Rep Max (1RM) Calculator
Enter weight lifted and reps completed to estimate your one rep max.
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1RM Percentage Chart
| Reps | % of 1RM | Training Zone |
|---|---|---|
| 1 | 100% | Max strength |
| 2–3 | 93–95% | Strength / peaking |
| 4–6 | 85–90% | Strength / hypertrophy |
| 7–10 | 75–83% | Hypertrophy |
| 11–15 | 65–73% | Muscular endurance |
| 15+ | <65% | Endurance / warm-up |
How to Estimate Your One Rep Max
Your one rep max (1RM) is the maximum weight you can lift for a single repetition. It is the foundation of percentage-based training programs.
Rather than testing a true 1RM (which carries injury risk), you can estimate it from a submaximal set. Lift a challenging weight for 3–10 reps and plug the numbers into the formula. The Brzycki and Epley formulas are the most widely used and validated.
The Epley formula (used here) estimates 1RM as weight × (1 + reps/30). Brzycki gives weight / (1.0278 − 0.0278 × reps). Both are accurate within 5% for sets of 2–10 reps; accuracy drops for sets above 10 reps, as fatigue affects the linear relationship between reps and percentage of max.
Example: lifting 185 lbs for 5 reps. Epley: 185 × (1 + 5/30) = 185 × 1.167 = 215.9 lbs → estimated 1RM ≈ 216 lbs. Brzycki: 185 / (1.0278 − 0.0278×5) = 185 / 0.889 = 208 lbs. Typical spread between formulas is 3–5%; the Brzycki formula tends to be more conservative.
Use your estimated 1RM to set training percentages: 70–75% for hypertrophy work (8–12 reps), 80–85% for strength (4–6 reps), 90%+ for near-maximal training. Most powerlifting programs prescribe percentages based on a "training max" set at 90% of true 1RM to build in safety margin.
Testing a true 1RM carries injury risk, especially for novices. Estimate from a well-executed 3-rep or 5-rep max at submaximal effort for safer, repeatable testing. Retesting every 4–6 weeks tracks progress accurately.
See also: Plate Loading Calculator · Progressive Overload Calculator