One-Rep Max

Your one-rep max, written 1RM, is the heaviest weight you could lift once with good form for a particular exercise. Strength programs are usually written as percentages of it, so a session might call for five sets of three at 80 percent.

Most people never test it directly, and that is sensible. A genuine maximum attempt needs a thorough warm-up, a spotter and a reason, and it leaves you tired for days. The usual approach is to estimate it from a set you have already done, using a formula that accounts for how the weight you can lift falls off as the repetitions go up.

The two common formulas are Epley and Brzycki. They agree closely at low repetitions and drift apart as the repetitions rise, with Epley the more generous of the two. Both are reliable up to about five repetitions and should be treated as rough above ten, because at that point you are measuring muscular endurance rather than maximum strength.

What it is not

An estimate is not a weight to go and attempt. It is a figure for setting training percentages, and the set it came from matters: three to five repetitions taken close to failure gives a usable estimate, while a set of fifteen does not.

Where you see it in FitnessSyncer

Our one-rep max calculator estimates one from a set you type in, with both formulas shown. It cannot yet read your logged lifts, because strength apps send us the heaviest weight of an exercise together with the repetitions summed across every set, and those two numbers together would give a badly inflated answer.