One-Rep Max Calculator

Estimate the most you could lift once, from a set of multiple reps.

How the Math Works

The One-Rep Max Calculator uses the Epley formula to estimate your maximum strength: 1RM = weight × (1 + reps ÷ 30). This equation assumes a linear relationship between the weight lifted, the number of repetitions performed, and the theoretical maximum weight you could lift for a single repetition. By adding 1 to the ratio of repetitions to 30, the formula scales the input weight upward, accounting for the fact that lifting lighter weights for more reps still reflects an underlying capacity for heavier single lifts. For example, lifting 100 pounds for 5 reps yields an estimated 1RM of 116.6 pounds.

Practical Applications

To use this calculator, simply enter the weight you successfully lifted and the number of repetitions you completed in a single set. The formula automatically calculates your estimated 1RM, which serves as a benchmark for designing strength-training programs, tracking progress, or comparing performance across different exercises or time periods. Athletes and coaches frequently use 1RM estimates to set training loads, as percentages of 1RM (e.g., 80% for strength or 60% for endurance) guide safe and effective workout programming.

Day-to-Day Use

Knowing your estimated 1RM helps you set realistic fitness goals and monitor improvements over time without risking injury from attempting your true maximum lift. It also empowers you to adjust workout routines dynamically—whether you're preparing for a competition, building muscle, or rehabilitating an injury—by providing a data-driven reference point for weight selection and progression. Beyond the gym, this calculation supports smarter training decisions in everyday activities, from sports to manual labor, by aligning effort with measurable physical capacity.

Worked example

185 lb × 5 reps → ~216 lb.

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