One Rep Max Calculator
Estimate your one-rep max from a set of several reps, with training loads for every percentage of 1RM.
What is a one-rep max?
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition with good form. Strength programs often prescribe loads as a percentage of 1RM. Testing a true max is tiring and carries some injury risk, so most lifters estimate it from a heavier set of 2–10 reps.
The formulas
Epley: 1RM = w × (1 + reps ÷ 30) Brzycki: 1RM = w × 36 ÷ (37 − reps) Lombardi: 1RM = w × reps^0.10
Bench pressing 185 lb for 5 reps gives about 216 lb (Epley), 208 lb (Brzycki) and 217 lb (Lombardi). The average, about 214 lb, is a sensible estimate.
Accuracy
Estimates are most accurate between 2 and 6 reps and become less reliable above about 10. They also vary by exercise and person: endurance-oriented lifters can do more reps at a given percentage than powerlifters. Use the estimate to plan training, not as a target to test every week.
Using percentages in training
- Strength: 80–90% of 1RM for 3–6 reps.
- Muscle growth: 65–80% for 6–12 reps.
- Muscular endurance: under 65% for 15+ reps.
Always use a spotter or safety bars for heavy sets, and warm up gradually.
Frequently asked questions
Which 1RM formula is most accurate?
Epley and Brzycki are the most widely used and give similar results for 2–10 reps. Averaging several formulas smooths out their differences.
How often should I test my 1RM?
Most programs test or estimate every 4–12 weeks. Estimating from regular training sets avoids the fatigue of true max attempts.
Is a 1RM estimate safe for beginners?
Estimating from a moderate set is safer than testing a true max. Beginners should focus on technique before heavy loads.
Last reviewed Oct 20, 2026. Results are estimates; check important decisions with a qualified professional.