The Epley formula, and how far to trust it

The Epley formula estimates your one-rep max from a heavier set of a few reps: multiply the weight by one plus the reps divided by 30. A set of 5 at 200 pounds gives about 233. The estimate is close for a set of five or fewer and gets rougher as the reps climb, because people differ more in how many reps they can do at lighter weights.

Estimate yours

The formula

One-rep max = weight × (1 + reps ÷ 30).

A single is the max itself, so the calculator on this site returns the weight unchanged for one rep. Every extra rep adds a thirtieth of the weight. The formula traces back to a poundage chart Boyd Epley published in 1985 (opens in a new tab), not to a study.

Run backwards, the same formula says what share of your max a set of each rep count lifts.

How accurate it is

The formula is only as good as the set you feed it. A set taken close to failure tells it something. A set stopped well short of failure gives an estimate that is too low.

Rep count matters. In a 2006 study of 70 adults (opens in a new tab), a set taken to failure at five reps predicted the tested one-rep max better than a set of ten or twenty, and the authors advise using no more than ten reps to estimate a max. That is the reason the estimator above labels its rows as it does: closest up to five reps, fair up to ten, rough beyond.

The other reason is that people differ. A 2024 meta-analysis of about 7,000 people (opens in a new tab) found the spread between individuals in how many reps they can do grows as the weight gets lighter. On the bench press it put the average at about 4 reps at 90 percent of a one-rep max, 9 at 80 percent and 14 at 70 percent. The Epley formula expects a little fewer at each, about 3, 7 and 13. The averages are close, and individual lifters spread around them.

The same meta-analysis found lifters manage fewer reps at a given share of their max on the bench press than on the leg press. One formula for every lift is a simplification.

How it compares with other formulas

Several formulas do the same job. The most common alternative is Brzycki's. The two give the same answer at ten reps (opens in a new tab). Below ten, Epley gives a slightly higher estimate, and above ten the formulas drift apart. No formula fixes the underlying problem at high reps, which is that lifters differ.

Using it for working weights

A program that works from percentages needs a max, and most lifters do not test one often. Take a recent hard set of three to five reps, estimate the max from it, and work out the percentages from that. If the program uses a training max, take its percentage of the estimate, not of a tested max.

The rep table above does the same sum the other way round. It shows the weight that each rep count from 1 to 10 implies for your estimate. Use it to pick a weight for a set of eight, then let the set correct you. If eight comes easily, the next set goes up.