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.

The estimate combines two standard formulas. Epley: 1RM = Weight × (1 + Reps / 30). Brzycki: 1RM = Weight × 36 / (37 − Reps). The headline figure is the average of the two, and each is also shown on its own. A single rep is taken as your max as entered, and the calculator accepts sets of 1 to 15 reps; the further a set runs past about 10 reps, the less reliable any rep-based estimate becomes.

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.