One-Rep Max Calculator
Estimate your one-rep max from a recent hard set — with both classic formulas shown side by side, because an estimate pretending to be one exact number is a small lie.
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The math, shown
Epley (1985): 1RM = weight × (1 + reps ÷ 30). Brzycki (1993): 1RM = weight × 36 ÷ (37 − reps). Both were built from reps-to-fatigue data; they agree closely at low reps and drift apart as reps climb — which is why both are shown, plus their average.
Accuracy: validation work found rep-based equations track tested maxes well for the bench press and squat, and tend to underestimate the deadlift (LeSuer 1997). The tightest estimate comes from a fresh, honest set of 2–5 reps — not a grinding set of 10.
An estimated 1RM is for programming percentages, not for proving. Testing a true max is a separate skill with a spotter, a rack and a day built around it.
These are population formulas — a starting point, not a prescription. Your training history, sleep, stress and cycle shift the real answer. That is what the 9-axis Body Scan measures.
Sources
- Epley B. Poundage chart. In: Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985.
- Brzycki M. Strength testing — predicting a one-rep max from reps-to-fatigue. J Phys Educ Recreat Dance. 1993;64(1):88–90.
- LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. J Strength Cond Res. 1997;11(4):211–213.
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