Special Thanks:
Ben Nguyen : Thank you for helping with research and editing
Discover Your True Strength with the One-Rep Max Calculator:
This simple one-repetition maximum (1-RM) calculator uses several formulas to give users a good estimate of their 1-RM for a particular exercise. The formulas generally give the user the same result but diverge after ten reps as shown with the graph below. When measuring your 1-RM, it is considered best to use a weight you can perform for less than ten reps, as all of these formulas diverge after ten reps, as shown below.
Formulas:
The formulas used are Epley, Brzynki, Adams, Baechle, Berger, Brown, Kemmler et al., Landers, Lombardi, Mayhews et al., Naclerio et al., O’Conner et al., and Wathens. None of these formulas are mine, nor do I claim to own any of them. I created this calculator for the public to have access to a nice snappy calculator GUI and API that provides the outputs of all of these formulas. A 1997 study by LuSeur et al. showed that Brzycki, Epley, Lander, Lombardi, Mayhew, O’Conner, and Wathen were able to adequately predict 1-RM for untrained male and female college-aged students. However, all of these equations significantly underestimated the deadlift. Additionally, this study used submaximal weight that caused reps till fatigue to be less than 10 (Maddalozzo, 91). The LuSeur et al. study concluded that Maythew and Wathen's formulas most accurately predicted bench press 1-RM, while Wathens’ formula best predicted squat 1-RM.(Maddalozzo, 91). However, it is important to note that these were for untrained college-aged individuals. Based on these studies, the average and mode were included for ensemble model calculation when creating this calculator. So, the mode or average calculated from these formulas may provide the most accurate value for some lifters. As noted before, the purpose of this calculator is to provide the user with as much data as possible for predicting their 1-RM.
For Newer Lifters:
It may be best to use the smallest weight calculated by the formulas as your body has yet to adapt to the stress of heavy weight lifting. Using the lowest weight ensures safety and a gradual introduction to the demands of heavy lifting. The one rep max calculated is just an estimate, and safety should always be a top priority when lifting, so adequate warm-up and preparation are needed when attempting to one rep max.
For Advanced Lifters:
LIGHT WEIGHT BABY
Support My Journey:
If you feel generous and want to get me a coffee or pre-workout, you can donate to my patreon up above. I will be creating more projects related to weightlifting in the future and am currently creating something very exciting related to this calculator.
Citations:
One-repetition maximum. (2023, August 24). In Wikipedia. https://en.wikipedia.org/wiki/One-repetition_maximum Maddalozzo, G. (2002). Accuracy of seven equations for predicting 1RM performance of apparently healthy sedentary older adults.(link down below)
Formula Divergence:
Read More:
Wikipedia One Rep Max:
External LinkAccuracy of Seven Equations for Predicting 1-RM Performance of Apparently Healthy, Sedentary Older Adults - Terry M. Wood, Gianni F. Maddalozzo, and Rod A. Harter
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