One Rep Max Calculator
Estimate your 1RM from reps — Epley and Brzycki, plus a %-of-1RM table for programming.
Updated
Estimated 1RM
117 lb
Epley · Brzycki says 113 lb
- 100% · ~1 rep
- 117 lb
- 95% · ~2 reps
- 111 lb
- 90% · ~4 reps
- 105 lb
- 85% · ~6 reps
- 99 lb
- 80% · ~8 reps
- 93 lb
- 75% · ~10 reps
- 88 lb
- 70% · ~12 reps
- 82 lb
Estimates for general information, not medical advice. Consult a healthcare provider for personal guidance.
In short
How do I estimate a one-rep max from reps?
Epley's 1985 formula is weight times 1 plus reps divided by 30, so 100 for 5 reps estimates a one-rep max of 116.67. Brzycki's 1993 formula, weight times 36 divided by 37 minus reps, gives 112.5 on the same set. This tool shows Epley as the headline figure and Brzycki alongside it as a second opinion.
Both formulas are least reliable above about 10 reps, where reported prediction error widens sharply, so a hard set of three to six reps gives much the cleanest estimate.
How to use the one rep max calculator
Enter the weight you lifted and the reps you completed with it, and the tool estimates a one-rep max without you attempting a single maximal rep. The weight is treated as a bare number: the lb and kg toggle is a label and the maths never converts between systems, so 100 for 5 reps returns 116.67 in whichever unit you put in.
The defaults, 100 for 5, exist so you can watch both formulas work before replacing them. Two published equations run behind the page. Boyd Epley published his in the Poundage Chart in the Boyd Epley Workout in 1985; Matt Brzycki published his in the Journal of Physical Education, Recreation and Dance in 1993.
The tool reports Epley as the headline and Brzycki beside it, because agreeing on one number would hide how much these formulas can differ.
116.67
Epley estimate
100 lifted for 5 reps
112.50
Brzycki estimate
the same set, second opinion
4.17
The gap
the visible floor on precision
Feed it a real working set taken to failure or very close to it. Both equations assume the reps you entered were roughly all you had, and neither has any way to know otherwise. Stop with three reps left in reserve and the calculator reads that load as easier than it was, so the estimate lands low; let form break down before genuine failure and it lands high.
The lift matters too. Validation studies have repeatedly found that these equations behave differently across exercises, generally predicting better on smaller-range upper-body lifts such as the bench press than on the squat or leg press, where trained lifters often complete many more reps at a given percentage of their true maximum than the formulas anticipate.
Do
- Feed it a hard set of three to six reps taken to or very near failure
- Re-estimate every few weeks, because training moves the real number
- Use the percentage table to set training loads from the estimate
Don't
- Estimate from light sets above about 10 reps, where prediction error widens sharply
- Enter a set with several reps left in reserve, which pulls the estimate low
- Test an untrained true maximum when an estimate would do
Read the estimate, then read the gap. On a set of 100 for 5 reps Epley returns 116.67 and Brzycki returns 112.5, a difference of 4.17 that comes entirely from how each equation weights reps. That gap is not noise to be averaged away; it is a visible floor on how precisely anyone can infer a maximum from a submaximal set.
The two formulas happen to cross at exactly 10 reps, where both return 133.33 from a 100 lift, and on either side of that crossing they swap places: below 10 reps Epley reads higher, and above 10 reps Brzycki does. The table below sets them side by side for every rep count from 1 to 12 so the pattern is visible in one place.
The two rep-max formulas run side by side on the same 100-unit lift at every rep count the tool accepts. The final column reads the other way round, showing what percentage of the Epley estimate that 100 lift represents, which is the figure a percentage-based programme uses. The two formulas cross at exactly 10 reps and swap places on either side of it.
| Reps with a 100 lift | Epley estimate | Brzycki estimate | Gap between them | The 100 lift as a percent of the Epley max |
|---|---|---|---|---|
| 1 | 100.00 | 100.00 | 0.00 | 100.0% |
| 2 | 106.67 | 102.86 | Epley higher by 3.81 | 93.8% |
| 3 | 110.00 | 105.88 | Epley higher by 4.12 | 90.9% |
| 4 | 113.33 | 109.09 | Epley higher by 4.24 | 88.2% |
| 5 | 116.67 | 112.50 | Epley higher by 4.17 | 85.7% |
| 6 | 120.00 | 116.13 | Epley higher by 3.87 | 83.3% |
| 7 | 123.33 | 120.00 | Epley higher by 3.33 | 81.1% |
| 8 | 126.67 | 124.14 | Epley higher by 2.53 | 78.9% |
| 9 | 130.00 | 128.57 | Epley higher by 1.43 | 76.9% |
| 10 | 133.33 | 133.33 | 0.00, the two formulas cross | 75.0% |
| 11 | 136.67 | 138.46 | Brzycki higher by 1.79 | 73.2% |
| 12 | 140.00 | 144.00 | Brzycki higher by 4.00 | 71.4% |
How do you turn the estimate into training loads?
Below the estimate sits the percentage-of-one-rep-max table, and that is the part most lifters actually program from. It maps each percentage to the reps typically expected there and shows the load each percentage works out to.
- 100 percent
- about 1 rep
- 95 percent
- 2 reps
- 90 percent
- 4 reps
- 85 percent
- 6 reps
- 80 percent
- 8 reps
- 75 percent
- 10 reps
- 70 percent
- 12 reps
The loads are simply the estimated max times the percentage, so on a 116.67 estimate 90 percent is about 105 and a 5x5 in the 80 to 85 percent band sits between 93 and 99.
The other number lifters look up
Published protein guidance is written as grams per kilogram of body weight. The protein intake calculator applies those factors, including the one for building muscle.
Open the protein intake calculator →The formula, worked line by line
Two standard rep-max equations turn a submaximal set, a weight and the reps completed with it, into an estimated one-rep max. Boyd Epley published his in the Poundage Chart in the Boyd Epley Workout, Body Enterprises, Lincoln, Nebraska, in 1985. Matt Brzycki published his in Strength Testing: Predicting a One-Rep Max from Reps-to-Fatigue in the Journal of Physical Education, Recreation and Dance in 1993.
Epley is linear in reps, adding one thirtieth of the lifted weight for each rep completed. Brzycki is a rational function whose denominator shrinks as reps rise, so its output accelerates. That single structural difference is why the two agree exactly at one rep and at ten reps, and disagree everywhere else, with Epley higher below ten and Brzycki higher above.
Epley: 1RM = weight x (1 + reps / 30)
Brzycki: 1RM = weight x 36 / (37 - reps)
100 for 5 reps: Epley 116.67, Brzycki 112.50
training load = estimated 1RM x percentage- Epley, 100 x (1 + 5 / 30)
- 100 x 1.1667 = 116.67
- Brzycki, 100 x 36 / (37 - 5)
- 3,600 / 32 = 112.50
- The gap between them
- 4.17, the point of showing both
At a single rep both collapse to the weight itself, since one rep already is a one-rep max. At ten reps they meet exactly: Epley gives 100 x 1.3333 = 133.33 and Brzycki gives 3,600 / 27 = 133.33. Beyond that crossing Brzycki climbs faster, reaching 144.00 at twelve reps against Epley 140.00.
Accuracy is best at low reps and degrades as reps climb. Reynolds and colleagues reported in 2006 that prediction was more accurate from a 5RM load than from 10RM or 20RM loads on the chest press and leg press, and validation work on Brzycki has generally found it adequate up to about 10 reps.
Published error figures typically sit in the region of a few percent in the two-to-eight rep range and widen considerably beyond ten reps. The underlying reason is that reps-at-a-percentage varies enormously between individuals and between exercises, and no single formula with one coefficient can capture that. If you want the cleanest estimate, feed the tool a hard set of three to six rather than a light set of twelve.
The percentage table is how lifters turn an estimate into training loads. On a 116.67 estimate, 90 percent is about 105, 85 percent is 99, 80 percent is 93 and 70 percent is 82, so a 5x5 in the 80 to 85 percent band runs somewhere between 93 and 99 and lighter back-off work sits near 82.
The one practical habit that keeps the table honest: re-estimate every few weeks, because training moves the real number and an old estimate silently makes every percentage wrong.
Questions people ask
How do I calculate a one rep max from reps?
Take a weight you lifted and the reps you completed with it near failure, then apply Epley: one-rep max equals weight times 1 plus reps divided by 30. A set of 100 for 5 reps gives 100 times 1.1667, which is 116.67. The number is unit-agnostic, so it works identically in pounds or kilograms, and no conversion happens anywhere in the calculation. This tool runs that arithmetic for you and adds the Brzycki estimate of 112.50 on the same set as a second opinion.
What is the difference between the Epley and Brzycki formulas?
Epley, published in 1985, is linear in reps, adding one thirtieth of the lifted weight per rep. Brzycki, published in 1993 in the Journal of Physical Education, Recreation and Dance, is a rational function whose denominator shrinks as reps rise, so it accelerates. They agree exactly at one rep and again at ten reps, where both return 133.33 from a 100 lift, and disagree everywhere else. Below ten reps Epley reads higher, above ten reps Brzycki does. On 100 for 5 the gap is 4.17.
How accurate is a one rep max estimated from reps?
Most accurate in the low-rep range and progressively less so as reps climb. Reynolds and colleagues reported in 2006 that prediction from a 5RM load beat prediction from 10RM or 20RM loads, and validation work on Brzycki has generally found it adequate up to about 10 reps. Published error typically sits at a few percent between two and eight reps and widens considerably beyond ten. The reason is that reps-at-a-percentage varies enormously between individuals and between exercises, which no single-coefficient formula can capture.
How do I use the percentage table to program training?
The table maps each percentage of the estimated max to the reps typically expected there: about 1 rep at 100 percent, 2 at 95, 4 at 90, 6 at 85, 8 at 80, 10 at 75 and 12 at 70. The load in each row is simply the estimated max times that percentage. On a 116.67 estimate, 90 percent is about 105, a 5x5 in the 80 to 85 percent band runs between 93 and 99, and lighter back-off work sits near 82. Re-estimate every few weeks, because a stale max makes every percentage wrong.
Is it safe to test a true one rep max?
Estimating from a submaximal set exists precisely so that nobody has to find out. The whole point of Epley and Brzycki is to get a usable number without a maximal attempt, which is the lower-risk route by a wide margin. If a real one-rep max is tested anyway, that means a thorough warm-up, tight technique and either a competent spotter or set safety bars. Beginners should not test an untrained maximum at all and should work from the estimate. This page gives general training information, not personalised coaching or medical advice.
Sources
Where the constants and formulas on this page come from. Each line names the figure it backs.
The Brzycki reps-to-fatigue equation this tool implements.
Strength Testing: Predicting a One-Rep Max from Reps-to-Fatigue — Brzycki M, Journal of Physical Education, Recreation and Dance 64(1):88-90, 1993
That a prediction from a 5RM load is more accurate than one from a 10RM or 20RM load, which is why low rep counts are the reliable input.
Prediction of one repetition maximum strength from multiple repetition maximum testing — Reynolds JM, Gordon TJ, Robergs RA, Journal of Strength and Conditioning Research 20(3):584-92, 2006
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