1 Rep Max Calculator


(This is one of the tools we have created on the site to aid those that purchase The Muscle & Strength Training Pyramid book with their program set up. We have decided to make this one publicly available.)

The following calculator is designed to calculate a one repetition maximum (1RM) from a ‘rep max’. A rep max is the number of complete repetitions you can maximally perform for an exercise for a given number of reps.

Important Notes

  • Accuracy: The degree of accuracy will vary depending on your level of weight training experience. If you are an inexperienced trainee you will likely find that this calculation overestimates your 1RM. (You are able to lift less because your nervous system has not been trained to handle the load.)
  • Equation choice: There are a few different ways to calculate 1RM. I’ve found Brzycki calculation to be the most accurate in trained lifters, and so that’s the one I use with my clients. However it gets far less accurate the higher the reps go, so…
  • Rep range: Use 2-5RM ideally to gauge you 1RM from the calculation. Higher reps can be entered with decreasing accuracy.
  • Safety: When attempting a true rep max it is best to use a spotter. Experienced trainees will be able to accurately gauge a rep max when testing themselves by stopping one rep before failure. Just be sure to count the rep you didn’t do when plugging it into the equation. So, if you got 400 lbs for 5 reps, but are certain you could have gotten another rep, then be sure to input 6 reps, not 5, into the calculation boxes.
  • Exercise selection: This calculator works best for compound/multi-joint exercises, particularly barbell squats, deadlifts, bench presses, and overhead presses. If you choose to estimate 1RM for horizontal or vertical pulling, ideally you should use a barbell bench (seal) row and a weighted chin up or pull up with a full range of motion, adding the external load on the chin or pull up to your bodyweight (weigh in before performing) to get an accurate estimation for these exercises. Movements like bent-over rows and lat pulldowns are very difficult to hold form on while going to or near failure with heavy loads and aren’t recommended in the case of 1RM testing.
  • Units: Weight (w) is a factor of each formula, so the unit of measurement doesn’t matter.

Grab your copy of ‘The Muscle & Strength Training Pyramid’ books here.