Why use a 1RM Calculator

Finding your one rep max, also known as 1RM, is a good gauge of where you are in your weightlifting or powerlifting progress. Achieving a new personal record is a proud moment for any casual or serious lifters. However, you may not be in a position to test your maximum effort one rep max. Furthermore, it’s not recommended to test your 1 rep max in every workout. Here are some reasons to go for a max reps instead:

  • You have exerted yourself while warming up before hitting your 1RM
  • You have no spotter
  • You may injure yourself
  • Your current program does not recommend testing your 1RM

The biggest advocate for not maxing out every workout is the increased injury rate and the mental and physical toll on your body. In order for you to reap the benefits of lifting heavy weights (“going heavy”), you do not have to work up to a one rep max. Studies show your neurological adaptation as well as physical tearing of the muscle fibers can occur between 85% to 100%of your maximum effort. An anecdote tells us Soviet olympic lifters routinely trained around 75% to 85% of their max. They only go up to their 95% to 100% max once every week. (Note: If you want to talk about the Bulgarian method of maxing out every workout, that’s a different story)

For our Barbell Collective athletes, most do 75% of their strength work in the 70% to 85% maximum effort which builds a foundation when you need to max out every month or so.

If you track your progress typically through multiple reps and sets, you can easily input those numbers into one of our many one rep max calculators. All of the formulas that go into these calculators are different, and we’ve provided explanations of how the formulas are justified. Most of these formula are created by renowned researchers in physical sciences or long time powerlifters. Of course, 1rm calculators are used to predict how much you could lift but this is no exact science. However, keep in mind that training is not testing. You are training to build your strength for the future, not test your ego with multiple plates.

With that said, the best way to find your one rep max is to test it out at the gym but remember to 1) warm up and 2) have a spotter just in case you go over the 1RM! Use this 1 rep max calculator as a suggested weight to guide you. Push yourself and test your strength! You are your only limit.

If you would like to find out your relative strength compared to other lifters of different shapes and weight, try out Wilks Calculator. Also, when you try out any of our calculators, feel free to leave comments on the accuracy and which one seems to work best for you! If you want to lose weight safely, find out how many calories you are burning using our TDEE calculator

1RM Calculation Formula

  • Lombardi Formula

    The Lombardi Formula was published in a book by Lombardi but did not have any scientific citations.

    w = weight   r = repetitions
  • Brzycki Formula

    The Brzycki Formula was created by Matt Brzycki who is the Coordinator of Health Fitness, Strength and Conditioning Programs at Princeton University and first published the formula in the Journal of Health in 1993.

    w = weight   r = repetitions
    This 1rm calculator is more accurate with lower repetitions. We recommend you use this formula when your max effort repetition is lower than 5.

  • Epley Formula

    Boyd D. Epley, the Associate Director of Athletics at the University of Nebraska, developed the Epley formula in 1985.

    w = weight   r = repetitions
  • O’Conner Formula

    w = weight   r = repetitions
  • Wathen Formula

    In 1994, Dan Wathen developed the Wathen Formula in Essentials of Strength Training and Conditioning.

    w = weight   r = repetitions
  • McGlothin Formula

    James D. McGlothin, the Associate Professor of Industrial Hygiene and Ergonomics at Purdue University who specializes in ergonomics created the McGlothin formula in 1993.
    w = weight   r = repetitions