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One Rep Max Calculator

How this is calculated

Two formulas are in wide use. Epley multiplies the weight by1 + reps / 30. Brzycki divides by 37 − reps and multiplies by 36. Below about five reps they agree closely; above that Epley reads higher. Showing both is more honest than picking one and calling it the answer — your real max depends on how your body handles a single heavy attempt, which no formula can see.

Both formulas lose accuracy past roughly twelve reps, where the set becomes a test of endurance rather than strength. That is why this calculator stops at twelve. Use a set you took close to failure: an easy set of five tells the formula nothing about your ceiling.

The percentage table below the result is the part most people actually use. Programs are written in percentages of a max, so once you have an estimate you can read your working weights straight off the table instead of doing arithmetic between sets.

Every weight in that table is rounded to something you can actually load — 2.5 kg or 5 lb, one plate on each side of the bar. A figure like 87.3 kg is arithmetically correct and useless in a gym. If your plates differ, treat the table as a starting point and round to whatever is on the rack.

An estimate ages. Run it again when a set feels clearly easier than the numbers say, and keep the effort comparable each time: an estimate from a set taken to failure and one from a comfortable set are not measuring the same thing, so comparing them tells you nothing.

Source: Epley (1985); Brzycki (1993).