What is Estimated 1RM (e1RM)?

Estimated One-Repetition Maximum (e1RM) is a mathematical estimation of a lifter's maximum single-repetition capacity, derived from submaximal lifting performance. Rather than testing a maximum single lift to failure—which presents safety risks and severe neurological fatigue—e1RM calculations use formulas based on the relationship between weight, repetitions, and fatigue. The most common formulas include the Epley and Brzycki equations.

The Epley formula is expressed as: 1RM = w * (1 + r / 30), where w is the weight lifted and r is the number of repetitions. The Brzycki formula is expressed as: 1RM = w / (1.0278 - 0.0278 * r). Research indicates these mathematical models are highly accurate when the repetitions performed are low (typically fewer than 10 reps).

As repetitions exceed 10, individual muscular endurance variations make the formulas increasingly unreliable. In modern strength programs, e1RM is calculated dynamically after each training session to track strength progress and adjust training loads without needing frequent, taxing maximal testing sessions..