Is the One Rep Max Calculator free to use?

Yes. The One Rep Max Calculator is completely free, runs entirely in your browser, and requires no account or sign-up. Your inputs never leave your device.

One Rep Max Calculator

Estimate your 1RM from any set using proven formulas.

Quick answer

Your one-rep max (1RM) is the most weight you can lift once. It's estimated from a lighter set with formulas like Epley: 1RM ≈ weight × (1 + reps ÷ 30). The estimate gets less reliable above about 10 reps.

Your set

Units

Weight lifted

kg / lb

Reps completed

Estimated one-rep max

115 kg

Epley

117 kg

Brzycki

113 kg

85% (5-rep work)

97 kg

70% (10-rep work)

80 kg

Estimating without maxing

1RM formulas extrapolate from a submaximal set: Epley adds 1/30 of the load per rep; Brzycki divides by a shrinking denominator. Both are accurate within a few percent under 10 reps, and this calculator averages them. Testing a true max isn't necessary for programming.

Using percentages

Programs prescribe work as %1RM: strength lives at 80–90% for 3–6 reps, hypertrophy at 65–80% for 6–12. Recalculate every few weeks — the estimate is a moving target when training works.

Frequently asked questions

How does the One Rep Max Calculator work?: Your one-rep max (1RM) is the most weight you can lift once. It's estimated from a lighter set with formulas like Epley: 1RM ≈ weight × (1 + reps ÷ 30). The estimate gets less reliable above about 10 reps.
Is the One Rep Max Calculator free to use?: Yes. The One Rep Max Calculator is completely free, runs entirely in your browser, and requires no account or sign-up. Your inputs never leave your device.

Sources & methodology