One-Rep Max Calculator

Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition with good form. It is the standard measure of maximum strength and the basis for setting training percentages.

These formulas estimate your max from a submaximal set, so they are approximations — not measurements. They are most accurate for sets of 10 or fewer reps; high-rep sets tend to overestimate your true max.

They are three published formulas for the same estimate: Epley multiplies weight by (1 + reps/30), Brzycki uses weight × 36/(37 − reps), and Lombardi uses weight × reps^0.1. This calculator shows all three plus their average, which smooths out each formula's bias.

Training programs set weights as percentages of your 1RM — for example 5 sets of 5 reps at 80% — so a good estimate helps you pick the right weight for strength, muscle-growth, or endurance goals.

Max attempts are risky without experience and a spotter. Estimating from a lighter set of 3–10 reps is the safer option. These numbers are estimates for education — not medical advice.