About One Rep Max Calculator

This is a free, independent site with tools for people who lift weights. A small team of web developers who train in the gym runs it. We are not doctors, and we are not certified coaches. That is why every formula on the site points to the study or group it comes from, so you can check it yourself.

Our method

• One rep max. We use the seven formulas tested by LeSuer and others in 1997: Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner and Wathan. The written form of each one is shown on the home page. A set of 1 rep returns the weight you lifted.
• Percent charts. The reps at each percent come from the NSCA Training Load Chart, which was adapted from Landers in 1984.
• RPE. We follow the reps in reserve scale from Zourdos and others in 2016, where RPE 10 means 0 reps left and RPE 9 means 1 rep left. Reps done plus reps left gives the reps you could have done. We turn that into a percent of your max with the Brzycki formula.
• DOTS and Wilks. We use the exact coefficients and body weight limits from the OpenPowerlifting source code.

Testing

Before each release, automated tests check the math. They confirm that 100 kg for 5 reps gives 116.7 kg with Epley and 112.5 kg with Brzycki, that the Wilks coefficient for a 100 kg man is 0.6086, and that the RPE and DOTS results match hand math.

Limits

The tools give estimates. A formula cannot know your sleep, your technique or how much you have trained a lift. Research shows the estimates are best with 10 reps or fewer, and the deadlift is often underestimated. Use the numbers to plan, not as a promise.

Safety note. These numbers are estimates for healthy adults. They are not medical advice. Max lifts carry real risk. Warm up, use a spotter or safety bars, and stop if you feel pain. If you have a health condition, an injury or are new to lifting, talk to a doctor or a certified coach first. The Physical Activity Guidelines for Americans suggest muscle strengthening at least 2 days a week.

Your data

All math runs in your browser. Nothing you type is sent to us.

Updates

Last updated October 24, 2026. Found a mistake? Please tell us.

References

1. LeSuer DA et al. The accuracy of prediction equations for estimating 1RM performance in the bench press, squat, and deadlift. J Strength Cond Res. 1997;11(4):211-213
2. Training Load Chart, National Strength and Conditioning Association (NSCA)
3. Zourdos MC et al. Novel resistance training specific rating of perceived exertion scale measuring repetitions in reserve. J Strength Cond Res. 2016 (PubMed)
4. DOTS coefficients, OpenPowerlifting source code (dots.rs)
5. Wilks coefficients, OpenPowerlifting source code (wilks.rs)
6. Reynolds JM, Gordon TJ, Robergs RA. Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. J Strength Cond Res. 2006 (PubMed)