One-rep max calculator
One-rep max calculator: estimate your 1RM from any set
Enter a weight and how many reps you managed to see your estimated one-rep max (1RM), the most you could lift once. The result averages the two most used equations, Epley and Brzycki, and shows the spread across seven.
Estimate your one-rep max
Use a recent set done with good technique. Sets of 1 to 10 reps give the most dependable estimates.
Example: 100 kg × 5 reps
Estimated 1RM
114.6 kg
Epley
116.7 kg
Brzycki
112.5 kg
Range, 7 formulas
112.5–119 kg
Change the numbers and select Calculate to see your own estimate and a table of training loads.
How the estimate works
Each equation turns a set to failure into the load you could lift once. They were built from groups of lifters who did a set to failure and then tested their real one-rep max, so they describe an average lifter, not you exactly. Here is what each gives for 100 kg lifted 5 times:
| Equation | Formula (w = weight, r = reps) | 100 kg × 5 |
|---|---|---|
| Epley | w × (1 + r ÷ 30) | 116.7 kg |
| Brzycki | w × 36 ÷ (37 − r) | 112.5 kg |
| Lander | 100 × w ÷ (101.3 − 2.67123 × r) | 113.7 kg |
| Lombardi | w × r0.10 | 117.5 kg |
| Mayhew et al. | 100 × w ÷ (52.2 + 41.9 × e−0.055 r) | 119 kg |
| O’Connor et al. | w × (1 + 0.025 × r) | 112.5 kg |
| Wathen | 100 × w ÷ (48.8 + 53.8 × e−0.075 r) | 116.6 kg |
At low reps the equations agree closely. The further a set is from a single, the more they disagree, which is why a set of 3 to 6 reps gives a more dependable estimate than a set of 15. Brzycki wrote that his equation is only valid below 10 reps, and later studies agree: one comparison recommended using no more than 10 reps, and a study of 103 women found the equations more accurate when fewer than 10 reps were done.
Sets you didn’t take to failure
Most training sets stop short of failure, which is sensible. If you finished 5 reps but could have done 2 more, the set is really a 7-rep maximum. Choose the reps you had left under Reps left in reserve and the calculator adds them before estimating. Lifters judge reps in reserve fairly well when they are close to failure, and less well when many reps are left, so keep this to sets within about 3 reps of failure.
The RPE calculator uses the same idea for planning: it turns any set at a given effort into a load for the next one. Why stopping short of failure still builds muscle is explained in what the research says about training to failure.
Training loads from your 1RM
Programmes often prescribe work as a percentage of one-rep max. This table uses the example’s estimate; the calculator builds the same table from yours. The reps column is how many reps each load usually allows to failure, from the Brzycki equation.
| % of 1RM | Load (1RM 114.6 kg) | About this many reps |
|---|---|---|
| 100% | 114.6 kg | 1 |
| 95% | 108.9 kg | 3 |
| 90% | 103.1 kg | 5 |
| 85% | 97.4 kg | 6 |
| 80% | 91.7 kg | 8 |
| 75% | 86 kg | 10 |
| 70% | 80.2 kg | 12 |
| 65% | 74.5 kg | 14 |
| 60% | 68.8 kg | 15 |
How accurate is an estimated 1RM?
- It depends on the lifter. People differ in how many reps they can do at the same percentage of their maximum. In a 2024 meta-analysis the typical spread between people was about 2.5 reps at 80% of 1RM and 4.4 reps at 60%, so an equation can be several kilograms out for any one person.
- It depends on the exercise. The same percentage allows more reps on some lifts than others: at 80% of 1RM, about 13 reps on the leg press against 9 on the bench press in the same meta-analysis.
- Technique counts. A grinding last rep with a different bar path isn’t the same rep as the first. Use sets done the way you would attempt a single.
For tracking progress, the trend matters more than the exact number. If your estimate from similar sets keeps rising week to week, you are getting stronger, whether or not you ever test a true single.
Should you test a true 1RM?
You don’t need to. Testing a maximum takes careful warm-ups, good technique, safety bars or a spotter, and recovery afterwards. Beginners gain nothing from it that a 5-rep set can’t show. If you do test, work up in small jumps over several singles, stop when the bar speed drops sharply, and never test through pain.
Track your estimated 1RM in Bodyvault
The Bodyvault workout tracker works out an estimated 1RM for each lift from the sets you log (Epley, for sets of 10 reps or fewer) and charts it, so you can see strength rising without testing. It also logs reps in reserve and suggests the next weight from how your last session went. For the method behind adding weight or reps over time, read progressive overload, and use the plate calculator to load the bar.
Privacy
The calculation runs in this page. Nothing you type is sent to a server, saved in your browser or put into the address bar; reloading the page restores the example. The site’s usual behaviour is in the privacy policy.
Questions
Which one-rep max formula is most accurate?
None is best for everyone. Epley and Brzycki are the most widely used and give almost the same answer at 10 reps; they differ a little below that. Accuracy depends more on the set (fewer reps, close to failure, good technique) than on the formula.
How many reps should I use to estimate my max?
A set of 3 to 6 reps taken close to failure gives a dependable estimate. Above 10 reps, every equation becomes less accurate.
Is an estimated 1RM the same as my real max?
It is an estimate. In a study of 103 women, an Epley-type equation was right on average for sets under 10 reps, but individual estimates were often about 10% too high or too low. Your real maximum on a given day also depends on sleep, warm-up and practice with heavy singles.
Does it work in pounds?
Yes. Choose pounds and enter the weight in pounds; the result is in the same unit.
Can I use it for bodyweight exercises?
Only if you count the load you actually move, such as body weight plus added weight for pull-ups or dips. The equations were built from barbell lifts, so treat other exercises as a rough guide.
Sources
- Brzycki M (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. JOPERD 64(1):88–90.
- Lin TY et al. (2021). The effects of barbell resistance exercise on information processing speed and conflict-related ERP in older adults: a crossover randomized controlled trial. Sci Rep 11:9137. Its Table 1 lists the seven equations used here.
- Reynolds JM, Gordon TJ, Robergs RA (2006). Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. J Strength Cond Res 20(3):584–592.
- Mayhew JL et al. (2008). Accuracy of prediction equations for determining one repetition maximum bench press in women before and after resistance training. J Strength Cond Res 22(5):1570–1577.
- Nuzzo JL et al. (2024). Maximal number of repetitions at percentages of the one repetition maximum: a meta-regression and moderator analysis of sex, age, training status, and exercise. Sports Med 54(2):303–321.
- Zourdos MC et al. (2016). Novel resistance training-specific rating of perceived exertion scale measuring repetitions in reserve. J Strength Cond Res 30(1):267–275.
- Helms ER et al. (2016). Application of the repetitions in reserve-based rating of perceived exertion scale for resistance training. Strength Cond J 38(4):42–49.