How this calculator works
A one-repetition maximum is the most weight you can lift once with good technique. Testing it directly is tiring and carries some risk, so lifters often estimate it from a set taken close to failure. Each formula fits a curve to the way strength falls as reps rise. Epley adds one thirtieth of the rep count to the load. Brzycki uses a ratio that rises steeply as reps approach the maximum. Lombardi raises the rep count to a small power. The percentage table then works in the other direction, showing the weight for common training intensities and the rep count usually associated with each.
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 percentage = one-rep max x percentage / 100.
Worked example
An 80 kg set of five reps gives an Epley maximum of 80 x (1 + 5/30) = 93.3 kg. Brzycki gives 80 x 36 / 32 = 90.0 kg, and Lombardi gives 80 x 5^0.10 = 80 x 1.175 = 94.0 kg. Using the Epley value, 85 percent is 79.3 kg, which is close to the 80 kg set that produced the estimate.
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Frequently asked questions
Which formula is most accurate?
All three are estimates with individual error. Keep the same formula and the same rep range when tracking progress, because switching formulas can move the number by several kilograms. Sets of three to eight reps tend to give the most consistent estimates.
Should I test a true one-rep maximum?
Only with a spotter and sound technique. Many lifters never need to test a single and instead use an estimated maximum to set training percentages. If you do test, warm up thoroughly and build in small increments.
Why is my estimated maximum higher than what I can actually lift?
Estimates assume you took the set close to failure. If you stopped several reps short, the formula overestimates. Fatigue, technique and the time between sets also matter, so treat the number as a training tool rather than a competition result.
Does bench press style change the estimate?
Yes. Grip width, arch, bar path and pause technique all change how much weight moves. A touch-and-go set and a paused competition set are not directly comparable, so estimate under the same conditions you train.