One Rep Max Calculator: Avoid Mistakes In Workout Planning (2024)

Home > Calculators > One Rep Max Calculator: Use It To Design Your Workouts

  • Benjamin Jenks (NASM-CPT)
  • Last Modified On February 22, 2024

Fact Checked By Jim Markus

Use this calculator to estimate your 1 Rep Max. With this information, you can design more effective workouts. Just enter the weight you lifted for any exercise and the number of reps you did at that weight. Then, the 1RM calculator does the rest.


Enter how much you lifted and with how many reps to see your 1 rep maximum (1RM).

Weight lifted


Your Results

Trainer's Tip: Add your most recent personal best, opting for the lowest rep count to enhance accuracy. Remember, a higher number of reps (+8) may compromise precision.

P.S. If you have any questions or comments, please share them below, and we'll try to answer them or create more content to help. For example, we're curious how accurate 1RM calculators have been for you?

Table of Contents

How This 1 Rep Max Calculator Works

This One Rep Max (1RM) Calculator is designed for any lift and accurately estimates your max without risking a one rep test.

Now, you can plan your workouts with the correct weight to propel you toward your goals, whether that's strength, power, or size.

Instead of using the popular Epley or Brzycki formulas, our calculator draws on the research of Mayhew et al., which our research shows to be more accurate. It's also more complex, which is why our user-friendly calculator offers precision without the headache of crunching numbers (unless you're into that, in which case, dive into the details below).

If you need help designing your workouts, consider working with one of our strength coaches to get a custom program.

How To Plan Workouts with Your 1RM

Use your one-rep-max to determine how much weight to lift based on your goal.

  • For Strength, use 95% of Your 1RM: Get close to your 1RM to gain maximum strength. Sticking to 1 to 3 reps with a spotter for safety is ideal for breaking personal records.
  • For Power, use 90% of Your 1RM: This is essential for athletes seeking rapid force generation. Opt for explosive lifts at 3 to 4 reps, allowing sufficient rest for maximum power.
  • For Size, use 80% of Your 1RM: Hit the muscle-building sweet spot by balancing intensity and volume. Target 7 to 12 reps with minimal rest to stimulate muscle expansion.
  • For Endurance, use 70% of Your 1RM: Perfect for stamina, especially in endurance sports. Engage in no-rest circuits at 12 to 20 reps to boost intensity and metabolic rate.

This methodical approach empowers you to sculpt your training precisely, whether your goal is speed, strength, or stamina, by leveraging the strategic insights from your 1RM.

Do you want to increase your one rep max? Check out our full posts about how to increase bench press, squat, and deadlift strength.

The Science Behind Our Calculator

Most online one-rep max calculators use the formulas from Epley or Brzycki, which are based on a poundage chart from the 80s and a book from the 90s, respectively.

However, users have complained these calculators estimate too high.

That's why we went with the Mayhew formula, which is based on more extensive research from 2008. It also incorporates an exponential decay function relative to the number of reps, which is why it's been proven to be one of the most accurate formulas.

Mayhew et al. One Rep Max Formula:

One Rep Max Calculator: Avoid Mistakes In Workout Planning (1)
  • w is the weight lifted,
  • r is the number of repetitions performed
  • e is the base of the natural logarithm (approximately equal to 2.71828).

Mayhew considered the exponential relationship between the weight lifted and repetitions completed. This approach is tailored to reflect real human strength capabilities more accurately than linear models.

How many reps is best for powerlifting? Check out our full guide.


Is PR and one-rep max the same?

No, PR (Personal Record) and one-rep max (1RM) are not the same. A PR refers to the heaviest weight you've ever lifted in a specific exercise, representing your all-time best achievement. In contrast, a 1RM denotes the maximum weight you can lift right now, reflecting your current strength level. Although a PR and a 1RM can be identical, they may differ if, for example, your strength has decreased over time due to factors like aging.

What is a good 1RM for bench press, squat, and deadlift?

Check out the average strength standards for bench press, squat, and deadlift to see how your lifts compare with people your age and weight. For example, a 163-pound male who's 18 years old should be able to bench press 235 lbs, squat 361 lbs, and deadlift 425 lbs.

How to perform a 1RM Test?

To perform a 1RM test, warm up with light exercises. Start with a weight you can lift 6-10 times. Gradually increase weight in small increments, resting 3-5 minutes between sets until you find the maximum weight you can lift once but not twice. Always prioritize form and safety.


  1. Mayhew, J.L., Johnson, B.D., LaMonte, M.J., Lauber, D., & Kemmler, W. (2008). Accuracy of Prediction Equations for Determining One Repetition Maximum Bench Press in Women Before and After Resistance Training. Journal of Strength and Conditioning Research, 22, 1570-1577.
  2. RPubs – Playbook: Epley’s equations – include 1RM or not? [Internet]. [cited 2024 Feb 13]. Available from:
  3. Brzycki, Matt (1998). A Practical Approach To Strength Training. McGraw-Hill. ISBN 978-1-57028-018-4.
  4. Distasio T. Validation of the Brzycki and Epley Equations for the 1 Repetition Maximum Back Squat Test in Division I College Football Players [Internet]. Available from:
  5. Wood, Terry & Maddalozzo, Gianni & Harter, Rod. (2002). Accuracy of Seven Equations for Predicting 1RM Performance of Apparently Healthy, Sedentary Older Adults. Measurement in Physical Education and Exercise Science. 6. 67-94. 10.1207/S15327841MPEE0602_1.

Fact Checked By Jim Markus


One Rep Max Calculator: Avoid Mistakes In Workout Planning (2)

Hi! I’m Avi Silverberg and this is the place where myfriendsand I nerd out about powerlifting technique. On this blog we share all the things we wish we knew when getting started. On a personal level, I’ve been dedicating myself to the world of powerlifting for the past 15 years, having both competed and coached at the highest level.

  1. Benjamin Jenks (NASM-CPT) says: 5 months ago

    Hey guys, let us know your questions about how you can best implement this in your workouts!


  2. Duncan says: 4 months ago

    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: 4 months ago

      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: 3 months ago

      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: . Mayhew, the formula we used, has a lower error percentage there too.


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One Rep Max Calculator: Avoid Mistakes In Workout Planning (2024)
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