Rep Max Calculator

Instructions

Enter sets, reps, weight and optionally body weight for a set or series of straight sets that was at or near failure. To provide the most accurate estimation, sets should be below 5 and reps should be under 10. A recommended method for estimating your 1RM is testing your 3RM and then calculating your 1RM from that.

Body weight should be entered for exercises like pullups and dips, where a significant portion of the weight moved comes from your body weight. For even more accurate estimations, a percentage of body weight can be entered depending on the exercise. Pull-ups and dips move 95% of body weight, squats and deadlifts 77%, and push-ups about 68%. This will be integrated into the calculator in the future.

What's a rep max and why would I want to calculate it?

A repetition maximum is the most amount of weight someone can lift in one set for a given number of reps. For example, a one rep max (1RM) is the most amount of weight someone could lift for one rep and is the most commonly used rep max. It is often used in programs and workouts to determine how much weight you should be lifting, as in 80% of your 1RM. It's also often used in comparisons of absolute strength. When someone says they bench x amount of weight, they're most likely referring to their bench press 1RM.

Rep maxes can be directly tested. This is, unsurprisingly, the most accurate method. However, for maximal efforts like a 1RM, estimating them based on a submaximal effort is safer, easier, and less taxing.

How does this calculator work?

This calculator is largely based on the Epley formula. It can also account for the concept of actual resistance, so that exercises that move a significant portion of body weight can be more accurately estimated. For more information on the Epley Formula and 1RM estimation, check out this article on Wikipedia. For more information on actual resistance, check out this page on ExRx.

Why does it use the Epley formula?

While every formula for calculating 1RMs has its strengths and weakness, the Epley formula was chosen because it's one of the more accurate and straightforward formulas. It also does a decent job of predicting 1RMs using higher (>10) reps. If you're interested in other formulas and their accuracy, check out this paper by Mayhew et al.