Estimated 1RM

In plain words

An estimated one-rep max is a number a formula gives you. You put in the weight and the reps you did, and it returns a guess at the single you could manage. The usual formula is Epley's: weight × (1 + reps ÷ 30). Its use is comparison. Working sets of different weights and reps become numbers you can line up: 80 kg for 8 reps comes to 101.3, 85 kg for 5 reps to 99.2, so the lighter set was the better one. The guess loosens as the reps rise. A 2006 study of 70 adults found estimates from a 5-rep max the most accurate and advised using no more than 10 reps.

An example

Four sessions of bench press, all at 80 kg: 5 reps, then 6, 7 and 8. The formula reads 93.3, 96.0, 98.7 and 101.3 kg. The bar never changed, so the estimate rose 8 kg on reps alone. Read as a trend for that one lift it is useful. A 2026 preprint by Marzagão notes that the classic formulas came from small samples, mostly on the bench press, so an estimate is not a promise of what you would lift on the day.