Resources · 1RM Calculator
Strength tool

One rep max.

Estimate your 1RM from a working set. The Epley formula handles 1–10 reps (where it's most accurate). Lombardi handles 11–15 reps with reduced accuracy. Above 15 reps the calculator won't return a number because the formulas break down.

This calculator estimates your 1RM from a working set. Only enter a weight you can lift with good form. The estimate is a guide for programming.

Inputs

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Enter a weight and rep count, then hit estimate. The percentage table will fill in below.

Safety note. Working at 90%+ of 1RM requires a spotter, safety pins, or both. There is naturally a higher risk of injury and is for advanced lifters only. If your form breaks, the rep doesn't count and the weight is too heavy. This calculator can be used to estimate 1RM without having to go beyond 90% yourself.