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One Rep Max Calculator

One Rep Max Calculator is part of Toolspire and is ready as soon as this page loads. Epley is weight × (1 + reps / 30). Brzycki is weight × 36 / (37 − reps). At one rep, Brzycki equals the weight and Epley is about 3.3% higher. Reps stop at 12.

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What you can do here

Two formulas, named

You can see the disagreement instead of trusting whichever calculator hid its formula.

They already disagree at one rep

Brzycki returns the weight you typed. Epley adds one thirtieth, so a single at 100 is reported as 103.3.

A rep cap

Past 12 the page stops, rather than printing a max that the formulas were not checked against.

The sequence

How to use the One Rep Max Calculator

  1. 1

    Use a set that was actually hard

    A weight you stopped early on will understate the max. These formulas assume the reps were as many as you could do with decent form.

  2. 2

    Stay at 12 reps or fewer

    If the set was 15, the page will refuse. That refusal is the formula’s range, not a broken box.

  3. 3

    Compare Epley with Brzycki

    If they are far apart, do not pick the larger one as the weight to load next session.

Worth knowing

  • One Rep Max Calculator on Toolspire: Epley: weight × (1 + reps ÷ 30). The headline is this estimate.
  • Brzycki: weight × 36 ÷ (37 − reps). At 1 rep Brzycki equals the weight. Epley at 1 rep is weight × 31/30, so 100 becomes 103.3.
  • 100 for 10 reps is an Epley max of 133.3. The formulas disagree more as the reps rise.
  • Reps above 12 are rejected. A 20-rep set is a conditioning set, not a reliable max test for these equations.

These are estimates of a single

Epley and Brzycki project a one-rep max from a set of several reps. They are curve fits, not a measurement. Even at one rep they do not match: Brzycki returns the weight, and Epley multiplies by 31/30. A true single also depends on sleep, warm-up and the lift. The page prints both numbers so a 10-rep squat is not turned into one unquestioned load. It will not tell you how to attempt that load.

FAQ

Questions about One Rep Max Calculator

Where does One Rep Max Calculator run?

One Rep Max Calculator runs in this tab on Toolspire. What you type or drop in is not sent to us and is not stored on a server.

What is the Epley formula?

Weight times (1 + reps / 30). Ten reps at 100 estimates 133.3.

What is the Brzycki formula?

Weight times 36 / (37 − reps). It is the second number, labelled in the detail.

Why do the two numbers differ?

They were fitted on different data. They already disagree at one rep: Brzycki stays on the weight, Epley multiplies by 31/30. The gap grows as reps increase. Treat the pair as a range.

Can I use this for a 20-rep set?

No. The page accepts 1 to 12 reps. Beyond that the estimate is too loose to print.

Keep going

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