One rep max calculator

Estimate your one-rep max (1RM) from any weight and rep count, plus a full training percentage chart.

Weight lifted

Reps performed

Estimated one-rep max (Epley formula)

% of 1RM	90%	80%	70%	60%	50%
Weight	—	—	—	—	—

How your 1RM is estimated

This calculator uses the Epley formula, one of the most common ways to estimate a true one-rep max without actually testing a single maximal lift, which carries injury risk when done without proper preparation.

1RM = weight × (1 + reps / 30)
Accuracy drops as rep count increases — estimates from sets of 10-15 reps are noticeably less reliable than from sets of 1-5 reps.
This is an estimate, not a guarantee. Actual 1RM depends on technique, fatigue, and the specific lift.

Using the percentage chart for training

Most strength programs prescribe work at a percentage of your 1RM rather than an absolute weight, since it scales automatically as you get stronger. Lower percentages (50-70%) are typically used for warm-ups, technique work, or higher-rep volume sets, while 80-90%+ is used for strength-focused, lower-rep training.

A note on safety

Estimating 1RM from a submaximal set is generally safer than testing a true single-rep max, but any heavy lifting should still be done with a spotter or safety equipment where appropriate, and with a warm-up. If you're new to a lift, prioritize form over chasing a higher estimated number.