Rep Max Conversion Calculator

About this calculator

A rep max is the heaviest weight you can lift for a given number of repetitions, and strength-training formulas let you convert a known rep max at one rep count into an estimated load at any other. The two most widely used are the Epley formula, 1RM = weight × (1 + reps/30), and the Brzycki formula, 1RM = weight × 36/(37 − reps); this calculator uses that relationship in reverse to solve for the weight you should be able to lift at your target rep count, not just your theoretical one-rep max.

Powerlifters and strength coaches rely on this conversion to program percentage-based training without constantly testing a true 1RM, which carries injury risk and fatigue cost — instead, they test a comfortable 5RM or 3RM and derive the rest of the training percentages from it. It’s also how programs prescribe “work up to your 8RM” or similar rep-range targets when an athlete’s most recent max was measured at a completely different rep count.