How it works
- The Epley formula multiplies the weight by one plus reps divided by thirty.
- It works best for sets of 1 to 5 clean reps and drifts high past 10.
- Warm up first and use a spotter or safety pins for heavy attempts.
Good to know
- Grinding reps, bad technique and fatigue change the real max.
- Most programmes rarely need a true single; percentages of the estimate train just as well.
- Nothing is stored or sent anywhere.
Standards and sources
Last reviewed October 10, 2026
Frequently asked questions
How accurate is it?
Within about 5% for sets of 1–5 clean reps; beyond 10 reps the estimate drifts high. Singles with grinders and bad technique break the formula.
What is the Epley formula?
One-rep max equals weight times one plus reps divided by thirty. It is the most-used estimate in strength programmes.
Is maxing out safe?
Only warmed up, with a spotter or safety pins, and never with pain. Most programmes rarely need a true single.