One Rep Max Calculator
Estimate your one-rep max (1RM) — the maximum weight you can lift for a single repetition — without attempting a risky max lift. Enter a weight and the reps you can perform with it, and see your estimated 1RM plus training percentages.
Formula reviewed for accuracy. Our methodology & sources
One Rep Max Calculator
fitness calculator
How It Works
Rather than risking injury attempting a true maximum, the calculator estimates your one-rep max from a submaximal set using the Epley formula, which scales the weight up based on how many reps you completed. It then derives common training percentages of that max, so you can see roughly what weight to use for strength, hypertrophy, or endurance work. Estimates are most accurate when your set is in the one-to-ten rep range; beyond that, endurance starts to skew the result.
Formula
Epley Formula: 1RM = weight × (1 + reps / 30)
Examples
100 kg for 5 reps
Estimated 1RM of about 117 kg.
Frequently Asked Questions
What is a one rep max?
Your one-rep max (1RM) is the most weight you can lift for one full repetition of an exercise. It is the standard measure of strength and is used to set training intensities.
How accurate is the 1RM estimate?
Estimates are most accurate in the 1-10 rep range. Above 10 reps, accuracy drops because endurance becomes a bigger factor than pure strength.
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