One-Rep Max (1RM) Calculator

What is One-Rep Max (1RM)

1RM is the maximum weight an athlete can lift for a single repetition with proper form in a given exercise (squat, bench press, deadlift, etc.). Knowing your 1RM allows precise planning of training weights for different goals — from building strength to improving endurance.

Why estimate 1RM instead of testing it directly

A true 1RM test means lifting your absolute maximum for one rep, which puts high stress on joints and connective tissue and increases injury risk, especially for beginners. Formulas let you estimate 1RM safely — just perform a set of a few reps with a moderate weight, and the calculator extrapolates the result.

Calculation formulas

• Epley: 1RM = weight × (1 + reps / 30) — simple and the most popular formula, works well for 1–10 reps.
• Brzycki: 1RM = weight × 36 / (37 − reps) — slightly more conservative, often more accurate at 2–6 reps.
• Average: arithmetic mean of both formulas — a compromise if you're unsure which formula to trust more.

How to use the percentage table

After calculating your 1RM, the calculator builds a table showing what weight to use for training different qualities.

• Strength (85–100% of 1RM, 1–5 reps): low reps with heavy weight, long rest between sets (3–5 min). Good for peaking strength cycles.
• Hypertrophy (65–85%, 6–12 reps): the classic range for muscle growth, rest 60–90 sec.
• Endurance (below 65%, 12+ reps): lighter weight, high reps, short rest — builds muscular endurance.

Limitations and accuracy

These formulas give a good estimate at 1–10 reps. The more reps in a set, the less accurate the prediction — beyond 12–15 reps, the error can reach 10–15%, since muscular endurance starts to play a bigger role than raw strength. The result also depends on technique, warm-up, and fatigue level — so treat it as a training-planning guide rather than an exact sports-science measurement.

This is an estimate. The most accurate 1RM value is determined by an actual test supervised by an experienced coach following proper safety protocols and warm-up.