Training

Calculate your one-rep max

Enter a weight and the reps you managed. The calculator estimates your 1RM and shows which weight matches which percentage.

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1 to 12 clean reps, as close to failure as possible.

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How it works

The heavier a weight is relative to your maximum, the fewer reps you can do. Formulas like Epley and Brzycki describe this relationship and work backwards from a set of several reps to a single maximum rep (1RM).

The calculator uses both formulas and shows their average as the main result. Up to about 10 reps they are close together; beyond that they drift apart and both become less accurate. How many reps someone can do at a given percentage also depends on the exercise, training experience and muscle fiber type.

The table converts your estimated 1RM into working weights. The reps next to them are the average of both formulas, calculated backwards and rounded. Treat them as a starting point and adjust by feel or with the RPE table.

Formula and source

Epley: 1RM = weight × (1 + reps / 30) Brzycki: 1RM = weight × 36 / (37 - reps) Result = average of both formulas (for 1 rep = weight)

Sources: Epley B., Poundage Chart, Boyd Epley Workout, 1985. Brzycki M., Strength Testing: Predicting a One-Rep Max from Reps-to-Fatigue, Journal of Physical Education, Recreation and Dance 64 (1), 1993.

Frequently asked questions

It is an estimate. With 3 to 8 clean reps close to failure, it usually lands quite near your true max. The more reps, the bigger the error, because endurance and how you feel that day play a larger role.

Epley and Brzycki are the most common formulas and give similar values up to about 10 reps. The average smooths out their small differences. If the two are far apart, that is a sign the set had too many reps for a good estimate.

Not for building muscle. An estimated 1RM is enough to turn the percentages in a training plan into weights. A true max attempt is mainly interesting for strength athletes and should only be done with a warm-up, clean technique and a spotter.

It works best for compound barbell lifts like squat, bench press, deadlift or overhead press. For isolation exercises and machines the formulas are less reliable, because the relationship between weight and reps is different there.

All results are estimates and do not replace advice from a doctor or dietitian.

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