One-rep max calculator

This page estimates a one-rep max from a set you already did. It does not ask you to test a true single. The form takes a load and a rep count and prints three published equations side by side: Epley, Brzycki, and Lombardi. The percentage row under the result is taken from the Epley number only.

What the three equations do with the same set

Epley multiplies the load by one plus the reps divided by 30. A true single is left as the load you typed. Brzycki divides the load by 1.0278 minus 0.0278 times the reps, and it is also left alone when the set was one rep. Lombardi multiplies the load by the reps raised to the power 0.1, including when the set was a single, where any number to the power 0.1 is not 1, so Lombardi will not echo a one-rep test back at you. That is a reason to ignore Lombardi when you already have a single, and a reason the page shows all three instead of pretending they are the same function.

The equations were built on sets taken near failure, and they drift once the rep count gets high. A set of 12 and a set of 3 at the same load are not equally informative. Use a set of roughly 3 to 10 reps that actually challenged you. A warmup of 135 for 10 does not belong in the form. Neither does a grinder rep that only moved because you bounced it.

How to use the percentage row

The chart lists 100, 90, 80, 70, 60, 50, 40, and 30 percent of the Epley estimate. Those are loads to write on a plan, not a ranking of your strength. Hypertrophy work often lives around 65 to 85 percent for sets that still have a rep or two in reserve. Heavier work for strength sits higher and uses fewer reps. The American College of Sports Medicine progression position stand treats a gradual rise in stress as the principle, not a weekly requirement to set a new max. The paper is ACSM progression models in resistance training.

If Epley and Brzycki disagree by a lot, the set was probably outside the range where both formulas are stable. Repeat the estimate from a different rep range next week instead of averaging two bad inputs. Do not attempt a true one-rep max off this page if you do not have a spotter and a setup you already know. The number is a planning figure. The tools hub holds the same form next to the other calculators.