One-Rep Max Calculator
Estimate your one-rep max from any weight and rep count using the Epley and Brzycki formulas.
What is a One-Rep Max Calculator?
Your one-rep max (1RM) is the heaviest weight you could lift for a single complete repetition. Testing it directly is risky and tiring, so most lifters estimate it from a lighter set taken close to failure, using a formula built from barbell training data.
The two formulas
Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps). The two agree closely for 1–5 reps and diverge somewhat at higher rep counts — Epley tends to read a touch higher, Brzycki a touch lower. Both are most accurate for sets of 10 reps or fewer, taken close to muscular failure.
How to use it
- Enter the weight you lifted and how many clean reps you completed (ideally within 1–2 reps of failure).
- Compare the two formula estimates — if they're close, that's a good sign your estimate is reliable.
- Use the percentage table to plan training weights for strength, hypertrophy or endurance-focused sets.
Both formulas lose accuracy above roughly 10 reps, since very high-rep sets are limited more by muscular endurance than by the pure strength a 1RM is meant to measure — for an estimate from a higher-rep set, treat the result as a rough ballpark rather than a precise number.
Want the "why" behind this tool? Read Why Your Estimated One-Rep Max Is Never Exact — and That's the Point.