1 Rep Max Calculator

One repetition maximum tests (1-RM) are popular for measuring muscle strength. It is a measure of the maximal weight a subject can lift with one repetition. Measuring 1RM has safety issues, so it is sometimes useful to estimate the 1RM using a calculator based on the number of times (greater than 1) that comeone can lift a certain weight. See more on One Rep Max Testing.

One rep maximum calculators are used to predict a one rep maximum lift. To calculate your 1 repetition max result, enter the weight lifted and the number of reps in the boxes below, and then click "calculate".This calculator applies for all exercises, and any measurement unit for weight.

weight lifted
number of reps


What does it mean? See information about 1 rep max.

This calculator is based on the formula derived by Boyd Epley in 1985, which is 1RM = weight x (1 + (reps / 30))



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