One-Rep Max Calculator

Estimate your one-rep max (1RM) for any lift from a weight and rep count, using three proven strength formulas plus a training percentage chart.

Your Lift
About the Formulas
  • Epley: 1RM = weight × (1 + reps / 30)
  • Brzycki: 1RM = weight × 36 / (37 − reps)
  • Lombardi: 1RM = weight × reps0.10

All three are well-established strength-training formulas. Differences between them are usually small at low-to-moderate rep counts and grow larger at higher reps.

Frequently Asked Questions

Instead of risking injury by testing a true 1RM, you lift a submaximal weight for several reps and the calculator estimates what you could lift for a single rep. It uses formulas (Epley, Brzycki, Lombardi) based on the relationship between weight, reps and fatigue.

No formula is perfect, and accuracy decreases as rep count rises. Epley tends to estimate slightly higher at high reps, Brzycki slightly lower. Most lifters find these formulas accurate to within a few percent for sets of 1-10 reps. This calculator shows all three plus an average so you can compare.

For the most reliable estimate, use a set of 1-6 reps performed to (or very close to) technical failure. Estimates from sets of more than about 10-12 reps become significantly less accurate because the formulas were not designed for high-rep, more endurance-oriented sets.

Once you know your estimated 1RM, percentage-based training lets you programme working weights for specific goals: roughly 85-100% for maximal strength (1-5 reps), 65-85% for hypertrophy/muscle building (6-12 reps), and below 65% for muscular endurance (12+ reps).

Testing a true 1RM carries a higher injury risk, especially without a spotter or coach, and is not necessary for most training goals. Using a calculator from a comfortable, well-controlled set of reps is a safer way to estimate your max for programming purposes.
Training Zones

Strength: 85-100% of 1RM, 1-5 reps

Hypertrophy: 65-85% of 1RM, 6-12 reps

Endurance: below 65% of 1RM, 12+ reps

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Disclaimer

This calculator is for general fitness and programming purposes only and is not a substitute for professional coaching. Always use proper form, a spotter where appropriate, and stop if you experience pain.