One Rep Max Calculator

From the weight and the number of reps, through a formula fitted to real lifting data. Epley, the most widely used, is weight × (1 + reps ÷ 30), so 100 kg for 8 reps gives 126.7 kg. Brzycki takes a different shape — weight × 36 ÷ (37 − reps) — and gives 124.1 kg for the same set. Both are on this page along with five more, which is the quickest way to see that the answer is a range rather than a figure.

Good enough to programme from at low reps, and increasingly vague above ten. The formulas were fitted on sets of roughly two to ten, and within that band they land within a few percent of each other. A set of fifteen is testing a different quality — muscular endurance — and the formulas start disagreeing by more than they agree, so this says so on screen rather than printing a confident number.

Epley if you have no reason to prefer another; it is the one most lifting apps and coaches use, so your numbers will match theirs. Brzycki reads slightly lower at high reps and some people find it fits them better. The practical answer is to pick one and keep it, because the useful thing is the trend across months, and switching formula moves your max by a few kilograms for no real reason.

Almost every strength programme is written in them: five sets of three at 85%, or a back-off set at 70%. The table turns your estimated max into the actual weight for each of those, and shows roughly how many reps that percentage should be worth — so if a programme calls for 80% and you cannot get the prescribed reps, the max is probably set too high.

Not often, and not alone. A true one rep max attempt is a maximal effort with the worst technique you will use all month, and it costs several days of recovery. That is the practical case for estimating: a set of five tells you nearly as much, you can do it inside a normal session, and you can repeat it often enough to see whether the number is moving.

Yes. The unit is only a label — a one rep max in pounds is worked out from pounds, with nothing converted — so switch it and every number on the page is in that unit. Nothing you type is sent anywhere; the arithmetic runs in your browser.