One Rep Max (1RM) Calculator

Knowing the heaviest weight you could move for a single rep gives every other number in your program a reference point. This estimator pins down that figure for any lift, which is what lets you assign training loads that match your intent and follow progress without guesswork. Alongside the headline number, it lays out training percentages across a range of rep targets, so you can steer a session toward strength, hypertrophy, or endurance in line with the latest 2026 athletic performance research.

At its core sits the Epley formula, a well-established and dependable approach to estimating a max: 1RM = Weight * (1 + (Reps / 30)). Because Epley can run high at lighter loads, sets carried past 10-12 reps draw on corrections borrowed from the Brzycki and Lombardi formulas. The system reads your input and picks whichever formula fits best, delivering the most reliable 2026-validated estimate for the numbers you entered.

Accuracy starts with the quality of the set you log. Perform your reps with clean technique and push close to muscular failure, since a set that stops well short of that point will understate your true ceiling. Steer clear of running the estimate right after a brutal session, when fatigue drags your performance down and warps the result. The trap to avoid is feeding in a weight and rep count completed with sloppy form, which inflates the estimate and sets you up for injury once you chase the heavier loads it suggests.