Free strength tool
Enter the weight you lifted and the reps you got, and this one rep max calculator estimates the most you could lift once. It runs seven formulas (Epley, Brzycki, Lander, Lombardi, O'Conner, Wathan and Mayhew), averages them, and gives you a percentage table for programming. Add the set's RPE if you stopped short of failure.
Works for bench press, squat, deadlift and overhead press, in kilograms or pounds. No account, no email.
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Your estimate shows here
Seven formulas side by side, the average, and a percentage table from 50% to 100%.
The basics
Your one rep max (1RM) is the heaviest weight you can lift for one full rep with good form. It is the standard measure of maximal strength, and programs are written as percentages of it: 5 sets of 5 at 80%, a top single at 90%, and so on.
You do not need to test it. A hard set of 2 to 6 reps predicts it closely enough for programming, and that is what this calculator does. If you track your sets in a log, you already have the inputs.
The maths
Each formula was fitted to a different group of lifters, so they disagree a little at low reps and more as reps rise. For 100 kg for 5, the spread runs from 112.5 kg (Brzycki, O'Conner) to 119 kg (Mayhew). The average sits in the middle and is the number to program from.
| Formula | Equation | Note |
|---|---|---|
| Epley | weight × (1 + reps / 30) | The Ultra+ app default. Linear in reps. |
| Brzycki | weight × 36 / (37 - reps) | Most accurate under 10 reps in Mayhew 1995. |
| Lander | 100 × weight / (101.3 - 2.67123 × reps) | Close to Brzycki at low reps. |
| Lombardi | weight × reps^0.10 | Runs high at 1 to 3 reps, conservative past 10. |
| O'Conner | weight × (1 + 0.025 × reps) | The most conservative of the seven. |
| Wathan | 100 × weight / (48.8 + 53.8 × e^(-0.075 × reps)) | Exponential; flattens at high reps. |
| Mayhew | 100 × weight / (52.2 + 41.9 × e^(-0.055 × reps)) | Fitted on bench press. Highest at 5 reps. |
When to test
Estimate, most of the time. A true max attempt costs a session of recovery, needs a spotter on bench and squat, and tells you the same thing a heavy set of 3 does within a few percent.
Test when the number itself matters: a meet, the end of a training block, or when your estimate has moved a lot and you want to confirm it. Beginners should not test at all for the first few months. Their technique changes faster than their strength, so the number is out of date by the next session.
In the app
The Ultra+ app shows your previous set and your best set on every set, and the best set is ranked by Epley 1RM. Epley is simple, is linear in reps, and lands close to the average of the other formulas in the 2 to 8 rep range where most training happens.
It does run high above 10 reps, which is one more reason to keep your estimate sets heavy. The calculator marks the Epley result so the number here matches the number in your log.
Programming
The percentage table converts your max into working weights. Roughly: 90% for singles and doubles, 85% for triples to fives, 80% for sets of 6 to 8, 75% for sets of 8 to 10, and 65 to 70% for sets of 12 to 15.
Two habits make this work. First, program from a slightly low estimate, so week one is doable and you have room to add weight. Second, re-estimate from your top sets every few weeks rather than from a one-off max, so the percentages track the lifter you are now. The progressive overload guide covers what to add and when.
RPE
RPE is rating of perceived exertion on a 1 to 10 scale, where 10 is a set you could not have added a rep to. Each point below 10 is one rep in reserve: RPE 9 is one rep left, RPE 8 is two, RPE 7 is three. Zourdos and colleagues published the lifting-specific version of the scale in 2016.
The calculator adds your reps in reserve to the reps you did, so a set of 5 at RPE 8 is scored as 7 reps to failure. Leave RPE blank if the set was an all-out set.
By lift
The same formulas, but each lift has its own habits that push the estimate up or down. Pick the lift in the calculator and use these notes when choosing the set to enter.
Pick bench press above and enter a paused set. Bench estimates are the most reliable of the four lifts, because the range of motion is short and the set is not limited by your breathing or your lower back. A set of 5 at RPE 9 gives a tight number. Touch-and-go reps, or a bench where the bar bounces, add 5 to 10 kg the formula did not earn.
Use the calculatorSquat estimates are honest at 3 to 6 reps and drift high past that, because high-rep squats are limited by breathing and bracing before your legs give out. Use full-depth reps you would count in a meet. If your top sets are 8 to 10 reps, add RPE so the calculator knows how far from failure you were.
Use the calculatorUse 5 reps or fewer. The deadlift has the highest ratio of grip and bracing fatigue to muscle fatigue, so a 10-rep set says more about your conditioning than your max. Each rep from a dead stop, no bouncing. Because the bar starts on the floor, a deadlift estimate is one of the few you can test safely once you have it.
Use the calculatorStrict reps only, with the bar starting at the collarbone and legs locked. Overhead press is the lightest of the four lifts, so a 2.5 kg jump is a large percentage and the estimate is more sensitive to rounding. A set of 3 to 8 reps works well. Anything with leg drive is a push press, and mixing the two makes your log useless.
Use the calculatorFAQ
Short answers to the questions people bring to a 1RM calculator.
Within about 5% for most lifters when the set is 2 to 6 reps taken close to failure. Accuracy drops as reps rise, because a 12-rep set tests endurance as much as strength. Sets of 10 or more can miss by 10% or more, so treat those results as a rough guide.
No single formula wins for every lift and rep range. In Mayhew's 1995 bench press study, Brzycki was the most accurate for sets of 10 reps or fewer, and averaging two equations reduced the error. That is why this calculator shows all seven and highlights the average, with Epley marked as the app default.
Use a set of 2 to 6 reps taken to failure or within one rep of it. That range is heavy enough to reflect maximal strength and light enough to be safe without a spotter. The calculator accepts up to 12 reps, but the further you go past 6, the wider the error.
RPE 8 means you had two reps left in the tank. The calculator adds those reps before running the formulas, so 100 kg for 5 at RPE 8 is treated as 100 kg for 7. That gives a higher, and usually more honest, estimate than pretending the set was a true failure set.
Yes, that is the main use. Take the average or the Epley number, then read the percentage table: 5 reps at about 85%, 8 reps at about 80%, 10 reps at 75%. Start a new block a little under the table, because an estimate can run high and you want room to add weight.
You rarely need a true test. Re-estimate every 4 to 6 weeks from a hard top set in your normal training, and update your percentages from that. Save actual max attempts for the end of a block or a meet, when you are rested and the lift has been practised heavy.
Yes. Pick kg or lb and every number, including the percentage table, comes back in the unit you entered. The table rounds to the nearest 2.5 kg or 5 lb, which matches the smallest plates in most gyms, so every weight it prints is one you can actually load on the bar.
Keep going
Ultra+ shows your previous set and your best set on every set, so the number to beat is on the screen while you train. The best set is ranked by the same Epley formula this calculator marks as the app default.
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