How the calculator works it out
The more reps you can do with a weight, the further that weight is below your one-rep max (1RM). Each formula turns a weight and a rep count into an estimated max. They are close for short sets and spread apart as the reps climb, so the calculator shows all three and uses their average.
Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Lombardi: 1RM = weight × reps0.10
Estimated 1RM = average of the three
A single rep is taken as your max for every formula. The "About" column in the chart turns Epley around, reps = 30 × (100 ÷ percent − 1), to show roughly how many reps each load allows. It is a guide, not a target.
Worked example: 225 lb for 5 reps
Epley gives 225 × (1 + 5 ÷ 30) = 262.5 lb. Brzycki gives 225 × 36 ÷ 32 = 253.1 lb. Lombardi gives 225 × 50.1 = 225 × 1.1746 = 264.3 lb. The average is 260.0 lb. For a working set at 80%, that is 208 lb exactly, which loads as 210 lb, good for about 7 to 8 reps. This set loads when the page opens.
Sources
- Brzycki. M. Brzycki, "Strength testing: predicting a one-rep max from reps-to-fatigue", Journal of Physical Education, Recreation and Dance, 1993;64(1):88–90.
- Epley. B. Epley, Poundage Chart, Boyd Epley Workout, Body Enterprises, Lincoln, NE, 1985.
- Lombardi. V. P. Lombardi, Beginning Weight Training, W. C. Brown, Dubuque, IA, 1989.
- How well they work. LeSuer and colleagues compared seven formulas, including these three, on the bench press, squat and deadlift (Journal of Strength and Conditioning Research, 1997;11(4):211–213). Predictions tracked real maxes closely for bench and squat but came in low for the deadlift.
- Training loads. The ACSM 2009 position stand on progression models suggests 8 to 12 rep loads for novices and 1 to 12 reps, with an emphasis on 1 to 6, for strength in trained lifters. The ACSM 2026 position stand found strength gains were greater with loads of at least 80% of 1RM.
Limits
- The estimate assumes the set was taken close to failure with good form. Stopping well short of failure makes it low.
- Rep-to-max relationships differ between lifts and between people. Your deadlift, for example, may allow more reps at a given percentage than your bench press.
- Use the number to plan training, not as a target to chase. For a full weekly plan, try the workout plan generator.
Questions people ask
How do I estimate my one-rep max without maxing out?
Pick a weight you can lift with good form for 3 to 10 reps, do as many clean reps as you can, and stop when the next rep would break down. Enter the weight and the reps. 225 lb for 5 reps gives about 253 to 264 lb depending on the formula, so roughly 260 lb.
Which one-rep max formula is most accurate?
No single formula wins for every lift and every person. Epley, Brzycki and Lombardi agree closely between about 3 and 10 reps and drift apart after that, which is why this calculator shows all three and their average. In a 1997 study by LeSuer and colleagues the formulas predicted bench press and squat well but underestimated the deadlift.
Why does the calculator warn above 10 reps?
The formulas were built from sets of roughly 10 reps or fewer. With longer sets, muscular endurance starts to matter as much as strength, so two people with the same max can get very different rep counts. Above 10 reps the three formulas also spread out, so treat the result as rough.
What percentage of my 1RM should I train with?
The American College of Sports Medicine suggests beginners use loads they can lift 8 to 12 times, and more experienced lifters train across 1 to 12 reps with an emphasis on heavy 1 to 6 rep loads for strength. Its 2026 review found strength improved most with loads of at least 80% of the one-rep max for 2 to 3 sets.
Why are the weights rounded?
So you can load them. Weights in pounds are rounded to the nearest 5 lb, the smallest jump with a pair of 2.5 lb plates, and kilograms to the nearest 2.5 kg, a pair of 1.25 kg plates. The exact figure is shown next to each one.
Is it safe to test a true one-rep max?
A true max test is hard on joints and is best done with a warm-up, a spotter or safety pins, and good technique. Estimating from a set of 3 to 10 reps avoids lifting the heaviest possible weight. If you are new to lifting, have a health condition or feel pain, get advice before testing.