One-Rep Max (1RM) is the gold standard for measuring maximal strength. It's used to prescribe training loads (e.g., "work at 75% of your 1RM").
Estimation Formulas
- Epley: 1RM = Weight × (1 + Reps/30)
- Brzycki: 1RM = Weight × 36 / (37 − Reps)
- Lander: 1RM = (100 × Weight) / (101.3 − 2.67123 × Reps)
Training Zones
Strength: 85–100% 1RM (1–5 reps). Hypertrophy: 65–85% (6–12 reps). Endurance: 50–65% (15+ reps).
Why Estimate Instead of Test Directly?
Testing a true 1RM carries injury risk, especially for beginners with imperfect form, and isn't practical to repeat often. Estimation formulas let you predict 1RM from a safer, higher-rep set (e.g., your max for 5 reps), then use that estimate to program percentage-based training without maxing out every week.
Formula Accuracy Varies by Rep Range
Estimation formulas are most accurate for sets of 10 reps or fewer — accuracy drops noticeably above 12–15 reps, since higher-rep sets are influenced more by muscular endurance than pure strength. For the most reliable estimate, test with a set you can complete in the 3–6 rep range.