How One Rep Max Is Calculated: The Science of Strength

1. The Brzycki and Epley Formulas

Your One-Rep Max (1RM) is the maximum weight you can lift for a single repetition. Standard calculators use validated formulas to predict this value safely from sub-maximal efforts: Epley Formula: 1RM = Weight × (1 + [Reps ÷ 30]) Brzycki Formula: 1RM = Weight ÷ (1.0278 - [0.0278 × Reps])

2. Practical Application in Training

Predicting your 1RM allows you to program working sets using specific percentages of your maximum strength (e.g., performing working sets at 80% of 1RM to build strength) without needing to test your absolute maximum.