Which formula is more accurate, Epley or Brzycki?

Neither is universally better. At low reps they nearly match, and at high reps Epley usually gives a bit more. Using both gives a sensible range instead of a single point.

How many reps should I use to estimate?

Between 2 and 10 reps close to failure. Single sets and very high-rep sets make the estimate less reliable.

Is estimating 1RM safer than testing it?

Yes. Attempting a true 1RM carries more injury risk, especially without a spotter. Estimating from a moderate set avoids the maximal load and still sets your training percentages.

Training6 min readMarcus HillUpdated 2026-08-19

What is a one-rep max (1RM) and how to estimate it

1RM sits at the heart of any strength program. Here is how to estimate it safely and use the percentages in your training.

The one-rep max, or 1RM, is the heaviest weight you can lift for a single clean rep. It is the base unit of strength. Training percentages are built from it, progress is compared to it and load is planned around it. The catch is that testing a true 1RM is risky.

Why 1RM is better estimated

A maximal single carries a higher injury risk, especially without a spotter. So most lifters estimate 1RM from a normal set taken close to failure. It is safer and accurate enough for planning.

Two working formulas

1RM = weight x (1 + reps/30)

Epley formula (1985), one of the most common one-rep-max estimates.

Epley, Boyd (1985)

1RM = weight x 36 / (37 - reps)

Brzycki formula (1993). Close to Epley at low reps and diverges at high reps.

Brzycki, Matt (1993)

For example, if you lifted 100 kg for 5 reps, Epley gives 100 x (1 + 5/30), about 117 kg. Brzycki gives 100 x 36 / 32, about 112 kg. Use them as a range, not one exact figure.

How to use 1RM percentages

About 85 percent of 1RM is roughly 6 reps.
About 75 percent is roughly 10 reps.
About 90 percent is roughly 4 reps.

Frequently asked questions

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