How to estimate your one-rep max without testing it

2026-10-10 · Pensum

A true one-rep max is a risk and a bad day away from a missed lift. A good set of five to ten gets you almost the same answer.

The formula

Pensum uses the Epley formula: weight × (1 + reps ÷ 30). Lift 80 kg for 8 clean reps and your estimated one-rep max is 80 × (1 + 8 ÷ 30), which is about 101 kg.

When to trust it

It is most accurate between 2 and 10 reps. Past that, fatigue and not strength decides when you stop, and the estimate drifts. Use a set taken close to failure, with the same form you would use on a heavy single.

What to do with the number

• Pick working weights as a share of it. A set of 8 sits around 75 to 80 percent.
• Track it over weeks. A rising estimate on the same lift means you are getting stronger, even if you never test a max.
• Re-estimate when your reps change, not on a schedule.

Try it with your own numbers in the 1RM calculator. In Pensum, every set you log updates the estimate and flags a new personal record for you. See the bench press and deadlift pages for how each lift is done, and the glossary for the terms.