One-Rep Max (Epley)

The Epley equation estimates the heaviest weight you could lift once by scaling up a lighter set performed for multiple reps. It is based on the idea that, for moderate rep ranges, each extra rep is associated with a fairly consistent drop in the percentage of maximal force you can produce, so the formula gives a practical approximation of 1RM rather than a true physiological measurement. It is most reliable when the set is taken close to failure and the reps are not too high.

Use this when you want a quick estimate of maximal strength without attempting a true one-rep max, such as during training planning or progress tracking. It is especially useful for common gym lifts like the bench press, squat, deadlift, and overhead press.

• Using reps that were far from failure, which makes the estimate too low
• Applying the formula to very high rep sets, where the estimate becomes less accurate
• Confusing the estimated 1RM with an exact tested maximum