One Rep Max Calculator

Lift a weight for as many good reps as you can (ideally 3–6), then use a formula. The Epley formula is 1RM = weight × (1 + reps ÷ 30), so 100 kg for 5 reps estimates about 117 kg. This calculator averages 7 published formulas for a more balanced estimate.

For sets under 10 reps, Epley and Brzycki are the most widely used and agree closely. Accuracy drops as reps increase because endurance varies between people — that's why the tool shows the range across formulas.

Roughly 85–95% for 1–5 reps builds maximal strength, 65–85% for 6–12 reps suits muscle growth (hypertrophy), and under 65% for 15+ reps builds muscular endurance. Warm-ups usually start around 40–50%.

Testing a true max stresses joints and technique, so beginners are better off estimating from a 3–5 rep set. If you do test, warm up thoroughly, use a spotter or safety bars, and stop when form breaks down.

As a rough guide, an intermediate male lifter benches about 1–1.25× body weight and an intermediate female lifter about 0.5–0.75×. Standards vary a lot with age, training years and height.

Training weights are rounded to the nearest 2.5 kg or 5 lb so you can actually load them with standard plates.