Estimate your one-rep max without testing it.

What is a one-rep max and why does it matter?

A one-rep max (1RM) is the heaviest weight you could lift for a single complete repetition of an exercise. It's used as a reference point for programming training intensity, since many strength programs prescribe work sets as a percentage of 1RM (like 80% for 5 reps) rather than an absolute weight, letting the program scale automatically as a lifter gets stronger.

How accurate is the Epley formula?

Reasonably accurate up to around 10 reps; accuracy declines as rep count climbs higher since the relationship between reps-to-failure and fatigue becomes less linear at high rep ranges. The Brzycki formula (1RM = weight × 36 ÷ (37 − reps)) is a common alternative that can differ slightly from Epley, especially at higher rep counts — for the worked example below, Brzycki gives roughly 208.1 versus Epley's 215.8, a reminder that any formula-based estimate has some built-in uncertainty.

Should I actually test my 1RM by lifting it?

Actual maximal-effort single-rep testing carries real injury risk, especially without a spotter, proper warm-up, or for lifters newer to a movement's technique. Most structured programs use an estimated 1RM from a comfortably submaximal set — like this calculator provides — rather than testing a true max directly on a regular basis.

How is this used in training programs?

Many strength programs prescribe work sets as a percentage of estimated 1RM — for example, 5 sets of 5 at 80% of 1RM — so lifters can scale intensity consistently as their strength changes over a training cycle, without needing to retest a true max repeatedly. See the reference table above for the equivalent weight at a few other common rep targets.

Worked example: lifting 185 lb for 5 reps: 1RM = 185 × (1 + 5 ÷ 30) = 185 × 1.1667 ≈ 215.8 lb. At that estimated 1RM, the weight for 3 reps would be about 196.2 lb, for 8 reps about 170.4 lb, and for 10 reps about 161.9 lb.