One Rep Max Calculator: Epley & Brzycki Estimates

 

Estimate a one-repetition maximum from a lifted weight and completed repetitions using the Epley and Brzycki formulas. These are rough estimates, not measured maximums or instructions to attempt a heavier lift.

Weight unitKilograms (kg)Pounds (lb)Lifted weightCompleted repetitions

Use the total external load for the set, including the bar when applicable. Enter 1 to 10 completed repetitions from one set. Changing Weight unit reinterprets the number entered; it does not convert it.

JavaScript is required for interactive estimates. Formulas and examples remain available below.

How to estimate one rep max

A one-repetition maximum, or 1RM, is the maximum load someone can lift once for a particular exercise under defined conditions. A formula estimates it from a submaximal set, but exercise technique, fatigue, training experience and how close the set was to failure affect the relationship.

Do not perform a maximum attempt just to fill in this calculator. Use a set you have already completed with appropriate technique. The tool does not assess injury risk, exercise suitability or readiness to lift.

Epley and Brzycki formulas

For sets of 2 to 10 repetitions, the Epley estimate is weight x (1 + repetitions / 30). The Brzycki estimate is weight x 36 / (37 - repetitions). Both return a result in the same unit as the entered weight.

At one repetition, this tool displays the actual entered weight for both formulas instead of applying an Epley uplift. This is an explicit single-repetition handling rule, not evidence that the lift was your maximum. For higher repetition sets beyond 10, the tool rejects the input rather than extending these estimates.

Worked example: 80 kg for 5 repetitions

Leave Weight unit at Kilograms (kg). Enter Lifted weight 80 and Completed repetitions 5, then select Estimate one rep max.

Epley gives 80 x (1 + 5 / 30) = 93.333333..., displayed as 93.33 kg. Brzycki gives 80 x 36 / (37 - 5) = 90 kg. The difference is 3.33 kg, rounded. This comparison does not show that your true maximum lies between the estimates.

Choose a consistent exercise and load

Use the same exercise, range of motion and load convention when comparing results over time. For a barbell lift, include the bar and plates in total external load. For dumbbells, be explicit in your own records about whether weight is per hand or combined, and keep that convention consistent.

This calculator does not add body weight for pull-ups or dips, adjust resistance bands, convert machine-stack labels into force or account for assisted repetitions. Those situations require additional assumptions. A machine or exercise change can make two estimates unsuitable for direct comparison.

Why estimates vary

The formulas describe simplified relationships between load and repetitions. Individuals and exercises differ in their repetition endurance. A set stopped well before failure may underestimate a maximum, while technique changes or inaccurate load entries can make the estimate misleading.

The calculator does not ask you to reach failure, recommend a training intensity or prescribe a progression. Treat results as rough tracking figures. An appropriate coach can help interpret performance and select training loads for your circumstances.

For a step-by-step walkthrough, read How to Estimate One Rep Max: Epley and Brzycki Formulas.

Units, limits and privacy

Lifted weight must be greater than zero and at most 10000 in the selected unit. This upper bound is a software limit, not a normal or recommended load. Repetitions must be a whole number from 1 to 10. Results round to two decimal places, with scientific notation for tiny positive values; displayed digits do not imply physiological accuracy.

Calculations run locally in your browser. This calculator does not save or send your entries. The hosting website may use separate analytics or advertising services.