A one-rep max is the heaviest weight you could lift once. Testing it takes a warm-up, several near-maximal attempts and a day of recovery, so most programs estimate it from a set that was already performed instead.
Estimate your one-rep max
Epley estimate70kg
Brzycki estimate67.5kg
What the numbers mean
Two published formulas, shown side by side on purpose. They disagree by a few percent, and seeing the gap is the honest version of the result: a single number would read like a measurement, and this is not one.
Both are at their best on a hard set of ten reps or fewer. Past that they drift away from tested maxima, so the calculator flags a high-rep set rather than answering as if nothing changed. Brzycki also has a hard edge: its divisor runs out at 36 reps, and beyond that it has no answer at all, which the calculator says instead of printing a number.
Reps only count if they were genuinely close to failure. Ten easy reps and ten hard ones give the same estimate here and very different true maxima.
The formulas, in words
- Epley: the weight, plus one thirtieth of it for every rep performed.
- Brzycki: the weight, times 36, divided by 37 minus the reps.
At a single rep both simply return the weight lifted, which is correct - a set of one already is the max.
How a coach uses it in Koach
Percentage-based programming is the usual reason to want this number: working sets written as a share of the max. Koach does not compute a one-rep max for you, so use the estimate here to pick the working weights, then write them into the plan.
Add the exercise and its sets in Create a workout plan, and once your client starts logging, their weight and rep history per exercise is visible in the app - which is a better source for the next estimate than the last one you ran.