How to Calculate Your One-Rep Max (Without Testing It)

What is a one-rep max, and why estimate it?

Your one-rep max (1RM) is the heaviest weight you can lift for a single clean repetition on a given lift. It is the number most percentage-based programs are built on: "3 sets of 5 at 80%" only means something if you know what 100% is.

You can find it by loading the bar until you miss. Most people should not do that often. A true max attempt is tiring, it tests technique at its worst, and one bad day gives you a number that is too low or, worse, an injury. The alternative is to estimate it from a set you were going to do anyway.

What is the Epley formula?

Epley is the most common one-rep max formula: multiply the weight by 1 plus the reps divided by 30.

1RM = weight × (1 + reps ÷ 30)

Take a set of 5 reps at 225 lb.

1. Divide the reps by 30: 5 ÷ 30 = 0.167.
2. Add 1: 1.167.
3. Multiply by the weight: 225 × 1.167 = about 262 lb.

What is the Brzycki formula?

Brzycki is the other common formula: multiply the weight by 36, then divide by 37 minus the reps.

1RM = weight × 36 ÷ (37 − reps)

The same set: 225 × 36 ÷ (37 − 5) = 225 × 36 ÷ 32 = about 253 lb.

Which is more accurate, Epley or Brzycki?

Neither is more accurate across the board: they agree at 10 reps, and below that Brzycki reads a little lower. Both formulas are simple curves, not measurements of you. Epley's comes from a 1985 poundage chart for University of Nebraska athletes, and Brzycki's from a 1993 article on strength testing (see the sources below). They agree near 10 reps and separate on either side. Here is the same 225 lb bar across different rep counts:

At 10 reps they land on the same number, because both formulas treat 10 reps as 75% of your max (225 ÷ 300 = 0.75). Below that, Brzycki reads a little lower. Neither one is "right"; pick one and use it consistently so your numbers are comparable week to week.

How accurate is an estimated 1RM?

It is an estimate, and it gets less trustworthy as the rep count climbs. Three things move the error:

• Rep count. A set of 3 to 5 tells you much more about your max than a set of 15. Past about 10 reps, endurance and pacing start to matter as much as strength. Researchers who tested these equations on the bench press and leg press concluded that no more than 10 reps should be used (Reynolds et al., 2006).
• How close to failure you took it. The formulas assume your last rep was a true grind. If you stopped with two reps left in the tank, the estimate comes out too low.
• The lift and the lifter. People who are strong in higher-rep ranges tend to get overestimated; people built for heavy singles tend to get underestimated. Squat, bench and deadlift also behave differently: a 1997 study that tested seven equations found that they underestimated the deadlift (LeSuer et al., 1997).

Treat the result as a working number for setting weights, not a personal record you can claim.

How do you use your one-rep max?

Multiply it by your program's percentages to get the weights to put on the bar. If your estimated squat 1RM is 262 lb, then 85% is 262 × 0.85 = about 223 lb. Round to the nearest weight you can actually load. If you are not sure how to build that weight from plates, see barbell plate math. To see how that number compares for your age and bodyweight, use the strength standards calculator.

Re-estimate whenever you hit a rep record on a lift, or every few weeks. Your working weights should follow your strength up, not sit at the number from three months ago.

Should you ever test a true max?

Sometimes. If you compete in powerlifting, or you want a real number for a meet or a milestone, a proper max attempt makes sense. Do it fresh, after a full warm-up, with safeties or a spotter, and not at the end of a hard session. For everyone else, an estimate taken from a solid set of 3 to 5 reps gets you nearly all of the benefit at a fraction of the risk.

Sources

• Brzycki, M. (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance, 64(1), 88-90. doi:10.1080/07303084.1993.10606684
• Epley, B. (1985). Poundage chart. In Boyd Epley Workout. Lincoln, NE: Body Enterprises. This chart is the origin of the Epley formula.
• LeSuer, D. A., McCormick, J. H., Mayhew, J. L., Wasserstein, R. L., & Arnold, M. D. (1997). The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. Journal of Strength and Conditioning Research, 11(4), 211-213. doi:10.1519/00124278-199711000-00001
• Reynolds, J. M., Gordon, T. J., & Robergs, R. A. (2006). Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. Journal of Strength and Conditioning Research, 20(3), 584-592. doi:10.1519/00124278-200608000-00020

The numbers in the tables on this page were recalculated from the two formulas above.