One Rep Max Calculator

The Epley and Brzycki formulas

A one-rep max, or 1RM, is the most weight you can lift for a single repetition. Rather than testing it directly, you can estimate it from a heavier set of several reps. The Epley formula is 1RM = weight × (1 + reps ÷ 30). The Brzycki formula is 1RM = weight × 36 ÷ (37 − reps). Both take the weight you lifted and the number of clean repetitions and project the load you could handle for one. This page shows each estimate and their average.

The two formulas agree almost exactly at very low reps and drift apart as reps climb, which is why seeing both is useful. Estimates are most dependable between about two and ten reps. Above that, fatigue, pacing and technique introduce more error, so treat high-rep predictions as rough.

Using the percentage table

Most strength programs prescribe loads as a percentage of 1RM. The table converts your estimated max into common training percentages and a rough rep guide: heavy work near 90% builds maximal strength for low reps, the 70–85% range drives hypertrophy for moderate reps, and lighter loads around 60% suit higher-rep and technique work. Use these as starting points and adjust to how the bar actually moves on the day.

Train smart and a safety note

Because a true max attempt is risky, estimating from sub-maximal sets lets you program heavy training while keeping a rep or two in reserve. Always warm up thoroughly, use good form, and add a spotter or safety pins for big lifts. Strength varies with sleep, nutrition, fatigue and the specific exercise, so an estimate from one lift will not transfer perfectly to another. This page is for general information only and is not medical or coaching advice. All math runs locally in your browser and nothing is uploaded.