4 thoughts on “One Rep Max Calculator: Use It To Design Your Workouts

  1. Duncan says:

    I know you say this is more accurate that other one rep max calculators. But how accurate is this?

    1. Benjamin Jenks (NASM-CPT) says:

      Good question! To make it as accurate as possible, take a lift where you’ve done less than 5 reps. Use the calculator to estimate your 1RM. Then you can plan your workouts with it and trust it’s accurate. After 1-2 months, then you’ll have enough feedback to make tweaks to make it even better.

    2. Jim Markus says:

      Most of the calculators you’ll find provide pretty similar results. We like Mayhew’s calculation because it falls closer to the mean in the studies we reviewed. The Brzycki and Lander formulas showed higher error percentages when evaluated in this study: https://www.unm.edu/~rrobergs/478PredictionAccuracy.pdf . Mayhew, the formula we used, has a lower error percentage there too.


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