1RM Calculator

How to Calculate Your One-Rep Max

To estimate your 1RM without testing it, take a set of several reps and run it through a formula. The Epley formula, the calculator’s default, is short:

1RM = weight × (1 + reps ÷ 30)

Example: 5 reps at 175 lb gives 175 × (1 + 5 ÷ 30) = 204.2 lb. With the Brzycki formula, the other common one, the same set gives 175 × 36 ÷ (37 − 5) = 196.9 lb.

Three pointers for choosing the set to enter:

• A set taken close to failure. The studies behind these formulas use sets taken to failure. If you stop with reps left in the tank, the estimate comes out lower than your real 1RM.
• 2 to 10 reps. The formulas were designed for this range, and they’re more accurate with 10 reps or fewer. Past that, the calculator stops showing an estimate.
• A max single is already your 1RM. If you lifted 225 lb once and couldn’t have done two, your 1RM is 225 lb, and there’s nothing to estimate.

The Seven 1RM Formulas

The calculator offers the seven formulas that two studies, in 1997 and 2002, compared against a measured 1RM. In the table, w is the weight and r is the number of reps.

Only one of these formulas was built on published data: Mayhew’s, in 1992, from 435 college students on the bench press. The others come from charts and textbooks that don’t say what population they’re based on:

• Epley: a weight chart published in 1985 in a training manual, not the result of a study.
• Brzycki: a 1993 article in a professional journal.
• Lander: a chart that ran in 1984 in the journal of the NSCA, the National Strength and Conditioning Association.
• Lombardi and O’Connor: two 1989 textbooks.
• Wathen: a chart published in a 1994 textbook, which other authors turned into an equation.

The calculator defaults to Epley because that’s the formula used by Log, a workout tracker for iPhone. For a set of 2 to 10 reps, you get the same number here as in the app.

Which 1RM Formula Is Most Accurate?

No formula comes out as the most accurate across all studies. The ranking changes with the exercise, the people tested, and the number of reps. Four findings keep coming up:

• Ten reps at most. The formulas are more accurate with 10 reps or fewer. In a study of 70 people, a 5-rep max predicted 1RM best, on the bench press and the leg press alike.
• Right on average, far off for some people. In a study of 103 women on the bench press, with 10 reps or fewer, most formulas landed within 2% of the measured 1RM on average. But the error varied a lot from one person to the next, and being 10% off the measured 1RM was nothing unusual.
• The exercise matters. Among 67 college students, all seven formulas underestimated the deadlift 1RM.
• The formulas don’t agree with each other. For 200 lb lifted 5 times, they give 225 to 238 lb.

So your estimated 1RM is a ballpark figure. You can use it to set your weights and track your progress, as long as you keep the same formula from workout to workout. It isn’t a measurement.

Rep Max Chart: Percentage of 1RM for 1 to 10 Reps

This chart shows what percentage of your 1RM you can lift for each number of reps. With a 1RM of 100 lb, the percentages are also pounds: your 5-rep max (5RM) is 86 lb with Epley and 89 lb with Brzycki.

The three columns don’t match because they don’t come from the same place. Two come from formulas. The third, the NSCA chart you see everywhere, is a rule of thumb. The NSCA itself says it’s adapted from a 1984 chart. The calculator’s table, at the top of the page, applies the formula you chose to your own 1RM. You can copy it or print it.

How Many Reps at Each Percentage of 1RM

The largest analysis to date, published in 2024, pools 269 studies and 7,289 people. It gives the average number of reps you can do, to failure, at a given percentage of your 1RM:

These are averages. At 80% of 1RM, it’s give or take 2 or 3 reps depending on the person. At 60%, it’s give or take 4 or 5. In this analysis, sex, age, and training level don’t clearly change the result. The exercise does. You get more reps on the leg press than on the bench press.

Against these numbers, the NSCA chart is about right on the bench press, but it gives too few reps at lighter weights and on the leg press.

What Your 1RM Is For

Programs often give weights as a percentage of 1RM or as a rep max: “4 sets at 80%,” “an 8RM.” Once you know your 1RM, you can turn either one into a weight.

In 2026, the American College of Sports Medicine updated its strength training recommendations, drawing on 137 research reviews. Strength improves more with weights of at least 80% of 1RM. Power improves more with 30% to 70%. Muscle growth improves more with higher volume, meaning 10 sets a week or more. You need a set close to failure to estimate your 1RM, but according to these recommendations, you don’t need to train to failure to make progress.

A percentage of 1RM comes from a past lift, and you aren’t equally strong every day. Reps in reserve (how many more reps you could have done) let you adjust the weight that day. The two methods work together. The RPE calculator gives the weight to use for a given number of reps and reps in reserve.

1RM for the Bench Press, Squat, and Deadlift

The calculation is the same for every exercise, but its accuracy isn’t.

• Bench press. It’s the most studied exercise. It accounts for 42% of the tests in the 2024 analysis, and the Mayhew formula was built on it.
• Squat. It’s less studied, at 12% of the tests in the same analysis. With a lot of reps, the formulas overestimate it. In 45 college football players tested at 17 reps on average, every formula gave a 1RM that was too high.
• Deadlift. In the 1997 study of 67 college students, all seven formulas underestimated it, so your actual 1RM may be higher than the estimate.

With a barbell, count the total weight, bar included. A 45 lb bar with 65 lb on each side is 175 lb. If your bar doesn’t weigh 45 lb, the barbell weight calculator has its weight, along with the plates to put on each side. For dumbbells and machines, the conventions are in the guide How to Log Sets, Reps and Weight.

1RM for Weighted Pull-Ups and Dips

On a bodyweight exercise, the total weight is what counts: your body weight plus the added weight. In studies, the 1RM of a weighted pull-up is the sum of the two (example).

Check “Include body weight” in the calculator. Example: you weigh 165 lb and do 5 pull-ups with 45 lb of added weight. The total weight is 210 lb and the estimated 1RM is 245 lb, or 80 lb of added weight for one rep.

One caveat: Log found no study that tests whether a formula like Epley’s gets the 1RM of a pull-up or a dip right. Studies do count body weight in the total, but running that total through the formula is Log’s choice. The guide How to Log Bodyweight, Added Weight and Assistance explains how to log these sets.

Test Your 1RM or Estimate It

• The test is reliable. A review of 32 studies concludes that a measured 1RM varies by only about 4% from one test to the next. The same review calls the test safe for very different groups of people. Individual studies still report frequent muscle soreness and, in older adults, injury rates of 2% to 19%.
• An estimate takes a single heavy set. Of 34 young men, 61% had muscle soreness after a 1RM test, and none did after a test of 4 to 10 reps (2002 study).
• A set to failure has its risks too. Form breaks down with fatigue.

This page explains a calculation. It doesn’t replace medical advice or the supervision of a qualified professional.

Your 1RM in Log

Log is a workout tracker for iPhone. In each exercise’s details, the “e1RM” (estimated 1RM) chart keeps the best estimate from each workout, calculated with the Epley formula from your sets of 10 reps or fewer. For pull-ups and dips, Log counts your body weight from your latest weigh-in, plus the added weight.

There’s nothing to calculate. Log your workout, and the chart updates on its own.