One-rep max calculator: Epley or Brzycki, and the plates to load
Type a weight and the reps you lifted it for. The calculator estimates your one-rep max the way the Kiptly app does, and shows how to load the bar.
By Kiptly ·
On this page
From 1 to 1000
From 1 to 1000 reps
Estimated one-rep max
Enter a weight and the reps you did with it.
What the estimate is
A one-rep max is the heaviest weight you can lift once. You do not have to test it to know roughly where it sits: a set you have already done for several reps carries enough to estimate it, and that estimate is what this calculator gives.
The Kiptly app works out the same estimate from the sets you log, and keeps the best one for each exercise among your personal records. Everything on this page comes from one set — a weight and a number of reps — so it is arithmetic, not a test, and it is only as good as the set behind it.
Two formulas, and where they meet
Epley’s formula multiplies the weight by one plus a thirtieth of the reps. Brzycki’s multiplies it by 36 and divides by 37 minus the reps. They agree at exactly ten reps. Below ten, Brzycki’s estimate is the lower of the two; above ten, the higher.
Brzycki’s has a hard edge: at 37 reps its divisor reaches zero, so the calculator — like the one in the app — takes at most 36 reps on Brzycki. Epley’s has no such edge, and it is the formula the app uses for the estimate it records.
The table under the result runs the chosen formula backwards. For every count from one to ten reps it shows the weight the same estimate predicts, and the row for the reps you typed gives back the weight you typed, whichever formula you choose.
Loading the bar
The last two columns turn each estimate into a weight you can put on a bar: the heaviest one at or under the estimate that the standard plates make, never above it. In kilograms that is a 20 kg bar with plates of 25, 20, 15, 10, 5, 2.5 and 1.25 kg; in pounds, a 45 lb bar with plates of 45, 35, 25, 10, 5 and 2.5 lb.
Those are the defaults of the plate calculator in the Kiptly app, where you can mark the bars and plates your own gym has, and the app then loads the bar from those.
Sources
Each source says how far we actually got into it. A citation list shows that a paper exists, not that anybody opened it — so this one is labelled.
Epley B. Poundage Chart. Boyd Epley Workout, 1985
The origin of the first formula, cited the way every strength text cites it. We have not read the original — it is a 1985 in-house training publication, not a journal article — and nothing on this page rests on it beyond the name.
Not read
Brzycki M. Strength testing — predicting a one-rep max from reps-to-fatigue
Journal of Physical Education, Recreation & Dance, 1993, 64(1), 88–90. The origin of the second formula. We have not read the paper; the page uses the formula and nothing else from it.
Not read
General fitness information, not medical advice.