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About This Tool
The One Rep Max (1RM) Calculator estimates the maximum weight you can lift for a single repetition based on the weight and number of reps you can perform. It uses the Epley formula, one of the most widely used and validated 1RM prediction equations.
The Epley formula is: 1RM = Weight × (1 + Reps / 30). This works best with rep ranges between 2-10 reps. The calculator also provides percentage-based training loads commonly used in strength programming.
Knowing your 1RM is essential for designing effective strength training programs. Most programs prescribe loads as percentages of 1RM: 60-70% for hypertrophy (muscle size), 75-85% for strength, and 90%+ for maximal strength and peaking.