Your estimated one-rep max (1RM) is shown using three formulas: Epley, Brzycki, and Lander. At low rep counts (1–5), these formulas tend to converge and produce similar estimates. As the rep count increases, the formulas diverge more, and accuracy decreases. The average of the three values provides a reasonable working estimate.

The 1RM is most commonly used to calculate training percentages. For example, hypertrophy-focused programs typically prescribe loads at 65–80% of 1RM (8–12 reps), while strength-focused programs use 80–95% of 1RM (1–5 reps). Many popular programs like Wendler's 5/3/1 use a training max (typically 85–90% of your estimated 1RM) as the basis for programming, which builds in a safety margin.

Use this calculator instead of testing your actual 1RM, which carries significant injury risk — especially for beginners or when training without a spotter. It is ideal for programming strength training percentages, tracking strength progress over time, and comparing relative strength across different exercises or training cycles.

It is most accurate when you use a recent set performed to or near failure with 1–10 repetitions. The closer the rep count is to 1, the more accurate the estimate. For best results, use a weight that represents a true effort — reps stopped short of failure will underestimate your 1RM.

All 1RM prediction formulas assume that the set was performed to genuine muscular failure with proper form. Reps stopped due to form breakdown, cardiovascular fatigue, or pain will produce inaccurate results. The formulas also assume a consistent relationship between submaximal reps and maximal strength, which varies between individuals and between exercises.

Accuracy decreases significantly above 10 repetitions. At 15+ reps, the estimates become unreliable because muscular endurance becomes a dominant factor rather than pure strength. The formulas were primarily validated on compound barbell lifts (squat, bench press, deadlift) and may be less accurate for isolation exercises or machine-based movements. Individual factors such as training experience, fiber-type distribution, and technique proficiency also affect the relationship between submaximal and maximal performance.