One Rep Max (1RM) Calculator

Estimate your one-rep max from weight and reps using the Epley formula.

Weight lifted kg

Repetitions reps

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Estimating strength with 1RM formulas

Last updated: March 30, 2026

A one rep max calculator estimates your maximum single lift from a submax set. This is safer and faster than testing true maxes frequently.

The Epley equation is widely used in strength training to map set performance into estimated 1RM and percentage-based training loads.

This helps lifters program sessions more accurately across intensity zones for strength, hypertrophy, and peaking blocks.

Frequently asked questions

How is 1RM estimated?

This tool uses the Epley equation: 1RM = weight × (1 + reps/30).

Is estimated 1RM accurate for high reps?

Accuracy tends to drop with very high rep sets. Estimates are most reliable around 1 to 10 reps.

Why use % of 1RM?

Programming by percentages helps structure strength, hypertrophy, and peak phases more consistently.