One Rep Max Calculator (1RM)
Estimate the heaviest weight you could lift once, from a lighter set.
Estimating your max safely
Testing a true one-rep max is hard on the body and risky without a spotter. These formulas estimate it from a set of several reps. They work best for sets of 10 reps or fewer, and different formulas give slightly different answers, so the calculator shows the average.
Example
With the starting values shown (Weight lifted 80; Repetitions completed 6), Estimated 1RM comes out as 94.9. Other results include epley: 96; brzycki: 92.9; lombardi: 95.7.
Strength coaches often prescribe training at a percentage of the one-rep max, such as about 80% for sets of around 8 reps. Your own results will vary with the exercise and your experience, and the estimate is less reliable for isolation exercises. Use good form, warm up, and train with a spotter when you lift heavy.
Frequently asked questions
Is the estimate exact?
No. It is typically within a few percent for small sets, but it can be off, especially for higher reps.
Which formula is best?
None is best for everyone, so this tool averages three.
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