How this calculator works
A one-repetition maximum, or 1RM, is the heaviest load a lifter can move once. Testing it directly takes a lot out of an athlete, so coaches use a set of several reps and a formula that describes how strength falls as repetitions rise. Epley multiplies the load by one plus the rep count divided by thirty. Brzycki divides thirty-six by thirty-seven minus the rep count. Lombardi raises the rep count to the tenth power. The three formulas agree closely for sets of about three to eight reps and diverge more outside that range. The percentage table turns the estimated maximum into training loads and pairs each percentage with the number of reps usually associated with it.
Formula
Epley: one-rep max = weight x (1 + reps / 30). Brzycki: one-rep max = weight x 36 / (37 - reps). Lombardi: one-rep max = weight x reps^0.10. Weight at a share of the maximum = one-rep max x share / 100.
Worked example
A 120 kg squat for five reps gives an Epley maximum of 120 x (1 + 5/30) = 140 kg. Brzycki gives 120 x 36 / 32 = 135 kg, and Lombardi gives 120 x 5^0.10 = 141 kg. Using 140 kg, 85 percent is 119 kg, which is close to the set that produced the estimate, and 70 percent is 98 kg for around twelve reps.
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Frequently asked questions
Which lift is easiest to estimate?
The squat and bench press are usually more predictable than the deadlift, because deadlift performance changes with grip, stance and floor speed. All estimates are best used as a guide and refined with experience.
How many reps should my test set be?
Three to eight reps is the usual sweet spot. A single rep is already a maximum test, and very high rep sets introduce muscular endurance and technique breakdown that the formulas do not capture.
Do I need to test my maximum directly?
No. Most training can be planned from an estimated maximum. A direct test is useful occasionally for a competition or a benchmark, but it should be done with a spotter and a proper warm-up.
Why do the three formulas disagree?
Each was fitted to a different group of lifters and a different rep range. The spread of a few percent is normal. Pick one formula and keep using it so that changes over time reflect training rather than a change of method.