How it works
The Epley formula estimates your one-rep max (the most weight you could lift for a single repetition) from a heavier set of multiple reps. This avoids testing an actual maximal attempt, which carries greater injury risk, while still giving you an estimate for programming training weights based on percentages of your 1RM.
1RM = weight × (1 + reps ÷ 30)
Worked example
A lifter completes 5 reps at 100 kg.
- reps ÷ 30 = 5 ÷ 30 = 0.1667.
- 1 + 0.1667 = 1.1667.
- 1RM = 100 × 1.1667 = 116.7 kg.
An estimated one-rep max of 116.7 kg.
Common questions
What is the Epley formula?
It's one of the most common formulas for estimating a one-rep max (the most weight you could lift once) from a set of multiple reps at a lighter weight, without actually testing a true 1RM attempt, which carries more injury risk.
How accurate is this estimate?
It's reasonably accurate for sets of about 2–10 reps. Below 2 reps there's nothing to extrapolate from, and above about 10–12 reps the formula tends to overestimate, since very high-rep sets test endurance more than raw strength.
Should I actually try to lift my calculated 1RM?
Not without appropriate spotting and warm-up — this is an estimate for programming purposes (e.g. setting percentage-based training weights), not a recommendation to attempt a maximal single lift based on the number alone.