Which formula does this use?

It averages the Epley and Brzycki formulas, two of the most widely used 1RM estimates, and shows each one separately. Estimates are most accurate for sets of about 10 reps or fewer.

What are the training percentages for?

Strength programmes often prescribe work as a percentage of your 1RM — for example 5 reps at 87% or 8 reps at 80%. The table converts your estimated max into target weights for common rep ranges.

Is my lift data uploaded?

No. The calculation runs entirely in your browser and nothing is uploaded or stored.

One Rep Max Calculator

Estimate your 1RM and training weights from a set you can do.

One-rep-max calculator

Your one-rep max (1RM) is the most weight you can lift for a single repetition. Rather than testing it directly, this calculator estimates it from a set you have already done — enter the weight and reps, and it averages the Epley and Brzycki formulas for a reliable figure.

You also get a table of training percentages so you can pick target weights for 1–12 rep work. Everything runs in your browser, nothing uploaded.