One-rep max calculator

Free Epley one-rep max calculator: enter a weight and reps to estimate your 1RM, or work out how many reps you can do at a target weight.

Questions

What is a 1RM?

Your one-rep max (1RM) is the heaviest weight you can lift for a single clean rep on a given exercise. It is the usual yardstick for strength, and training weights are often set as a percentage of it.

How accurate is the Epley formula?

Epley estimates 1RM as weight × (1 + reps ÷ 30). It is usually within a few percent for hard sets of about 10 reps or fewer, and gets less reliable as the reps climb. Treat the result as a good estimate, not a measurement.

What is the difference between Epley and Brzycki?

Both turn a weight and a rep count into an estimated 1RM. Brzycki uses weight × 36 ÷ (37 − reps); Epley uses weight × (1 + reps ÷ 30). They agree closely between 2 and 10 reps, and Epley reads a little higher on long sets.

Should I test my true 1RM?

Most lifters do not need to. A max single is hard on joints and technique, and a day of failed attempts costs training. A heavy set of 3 to 5 reps, run through a formula, tracks your strength well and is much safer to repeat.

Which rep count is best for estimating a 1RM?

Sets of 3 to 5 reps give the most reliable estimates. Singles and doubles are close to the real thing but demanding, and sets past 10 reps drift further from your true max because endurance starts to matter.