One Rep Max (1RM) Calculator

Our One Rep Max (1RM) Calculator helps you accurately estimate the maximum weight you can lift for a single repetition in any given exercise. Understanding your 1RM is crucial for effective strength training, allowing you to set appropriate training loads and track progress reliably. This tool also provides a comprehensive breakdown of training percentages across various rep ranges, helping you tailor your workouts for strength, hypertrophy, or endurance based on the latest 2026 athletic performance research.

This calculator primarily utilizes the Epley formula, a widely accepted and robust method for 1RM estimation: 1RM = Weight * (1 + (Reps / 30)). For higher rep counts (above 10-12 reps), we incorporate adjustments from the Brzycki and Lombardi formulas to ensure greater accuracy, as the Epley formula can sometimes overestimate at lighter loads. Our system dynamically selects the most appropriate formula based on your input to provide the most reliable 2026-validated estimate.

To get the most accurate 1RM estimate, ensure you perform your reps with good form and to near muscular failure for the given weight. Avoid using this calculator after an extremely fatiguing workout, as your performance will be compromised and the estimate inaccurate. A common mistake is inputting a weight and rep count that was performed with poor technique, which inflates the estimated 1RM and can lead to injury when attempting heavier loads.