One Rep Max Calculator

Estimate your 1RM from any working set, then use the percentage chart to program your training.

Weight lifted — kg

Reps completed

What Is a 1RM?

Your one-rep maxis the most weight you can lift for a single rep with good form. It's the standard for measuring absolute strength and the basis of nearly every serious program — 5/3/1, Texas Method, nSuns.

Brzycki Formula

1RM = weight × 36 / (37 − reps)

Most accurate at 10 reps or fewer. Beyond that, all estimation formulas diverge.

Training Zones

85–100% 1RM (1–5 reps): maximal strength
65–85% 1RM (6–12 reps): hypertrophy
60–70% 1RM (12–20 reps): muscular endurance

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