One-Rep Max Estimator
Updated .
This estimator turns a hard set into an estimated one-rep max (1RM) with two common equations, Epley and Brzycki, shown side by side with their midpoint. It also lists the loads at 60 to 95% of that estimate. Both equations are published for sets of fewer than 10 repetitions, and the further above five you go, the rougher the estimate. It is a planning figure, not a test result.
How it works
The estimator applies two published equations to one set:
- Epley: estimated 1RM = weight × (1 + reps ÷ 30). For a single repetition the estimate is the weight itself.
- Brzycki: estimated 1RM = weight × 36 ÷ (37 − reps). It cannot be used at 37 repetitions or more, and this tool stops at 30.
- Midpoint: the average of the two, shown so you have one number to plan with, plus the range between them so you can see how much the equations disagree.
- Percent table: the midpoint multiplied by 60, 65, 70, 75, 80, 85, 90 and 95 percent.
How far to trust it. A study of 70 men and women aged 18 to 69 (Reynolds, Gordon and Robergs, 2006) tested prediction from sets of 5, 10 and 20 repetitions on a chest press and a leg press. It found that the 5-repetition set predicted best and concluded that no more than 10 repetitions should be used in linear equations for those two exercises. The same paper lists Epley and Brzycki as intended for fewer than 10 repetitions. It tested a flat barbell bench press and a plate-loaded leg press, so how closely the estimate matches a squat, deadlift or overhead press for you is not reported here. The ACSM position stand notes that several methods exist for converting between percent of 1RM and repetition maximum without endorsing one, and that regular strength testing or perceived-exertion scales can be used to adjust loads as strength changes.
What the number is for. It gives you a starting load for the next block and a way to compare one month with the next. It is not a prediction of what you will lift on a heavy single. A set taken well short of the limit will under-estimate your max, and a set with loose form will over-estimate it.
Using the result by profile
For A You do not need a one-rep max in your first months. Choose a weight you can lift for 8 to 12 clean repetitions with some left over, and add load when that gets easy. Use this tool only to see roughly where you are heading.
For B Test a set of 3 to 6 on a main lift every few weeks, and track the estimate rather than any single day’s figure. Day-to-day readiness moves it.
For C Use sets of five or fewer for the estimate, record which equation you used, and compare like with like. Pair it with the RPE load calculator when you plan the week.
For D Give clients the range, not a single figure, and explain that it moves with sleep, stress and exercise choice. Do not set a heavy single from an estimate without a warm-up ladder.
For E Stay inside your clinician’s or physical therapist’s clearance. If you are returning from injury, do not use an estimate to choose a heavy attempt; use the load and repetition range you were given.
Worked example
Suppose a hypothetical set of 135 lb for 5 repetitions. Epley: 135 × (1 + 5 ÷ 30) = 135 × 1.1667 = 157.5 lb. Brzycki: 135 × 36 ÷ (37 − 5) = 4860 ÷ 32 = 151.9 lb. The midpoint is 154.7 lb, and 80% of that is 123.8 lb.
The two equations differ by 5.6 lb on this set, which is the honest size of the uncertainty here, before any day-to-day variation. These numbers are illustrative arithmetic, not a prediction for anyone.
Frequently asked questions
Which equation is more accurate, Epley or Brzycki?
This page does not rank them. The research it relies on lists both as meant for fewer than 10 repetitions, and the accuracy depends on the exercise and the person, so the tool shows both and their midpoint.
Why does the estimate get less reliable above 10 repetitions?
The published guideline for these equations is under 10 repetitions, and one study concluded that no more than 10 repetitions should be used in linear equations for the chest press and leg press. Long sets are also limited by endurance and discomfort, not just strength.
Should I test my true one-rep max?
Not necessarily. For most lifters an estimate from a hard set of three to six is enough to plan training, and a heavy single carries its own fatigue and technique demands. If you do test, use a spotter or safeties and a proper warm-up ladder.
Do the equations differ for women?
This tool applies the same arithmetic to everyone and does not show a separate version for women. The study cited above included both men and women; this page does not quote a separate result for women.
Does this send my numbers anywhere?
No. The calculation runs in your browser and nothing is stored or sent.
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