How it works: from one set to your max
You don't need to test a heavy single to learn your max. Enter a set you've completed, including the weight and rep count, and the calculator estimates your highest possible bench press for 1 rep. That figure is your one-rep max, shortened to 1RM.
Step one: the Epley formula
Epley is the formula behind the large figure under the form. The reasoning is simple: the more reps a weight lets you do, the heavier a single you could probably lift. Every extra rep moves the estimate up a little.
Imagine you bench press 225 pounds (lb) for 10 reps. Your max comes out near 300 lb with Epley. That's the main result since you can work it out by hand, and most bench calculators give the same number. Brzycki returns exactly the same answer at 10 reps.
Walk through the Epley calculation.
In full, Epley is max = (1 + reps ÷ 30) × weight. With 225 lb and 10 reps, that gives 300 lb.
Six more formulas for that set
Every one of the seven formulas is named after the researcher who published it. Your weight and your reps are where all seven begin. Each handles those numbers a bit differently, so the results spread apart. For 225 lb done 10 times, each one reports this.
| Formula | 225 lb × 10 |
|---|---|
| Epley | 300 lb |
| Brzycki | 300 lb |
| Lombardi | 283 lb |
| O'Conner | 281 lb |
| Wathen | 303 lb |
| Mayhew | 295 lb |
| Lander | 302 lb |
View each formula
The formulas below use w for the weight on the bar and r for your rep count.
| Formula | Equation |
|---|---|
| Epley | w × (1 + r ÷ 30) |
| Brzycki | w × 36 ÷ (37 − r) |
| Lombardi | w × r^0.10 |
| O'Conner | w × (1 + 0.025 × r) |
| Wathen | 100 × w ÷ (48.8 + 53.8 × e^(−0.075 × r)) |
| Mayhew | 100 × w ÷ (52.2 + 41.9 × e^(−0.055 × r)) |
| Lander | 100 × w ÷ (101.3 − 2.67123 × r) |
All seven appear on Wikipedia's one-rep max page, along with the paper that first printed each one.
Did those results match real bench maxes?
In a 1997 study, all seven formulas were tested against each person's true heaviest single. The bench press was covered, along with the squat and the deadlift. Its 67 participants were college students new to lifting, and no one went past 10 reps in a set.
| Formula | How far off from the real bench max |
|---|---|
| Mayhew | 0.8% |
| Wathen | 0.8% |
| Epley | 1% |
| Lander | 3% |
| Lombardi | 3% |
| Brzycki | 4% |
| O'Conner | 6% |
Mayhew and Wathen landed closest. The remaining five landed slightly below those real maxes. The source is LeSuer and colleagues' 1997 research.
Every formula falls short somewhere. So your result lists the lowest and highest answers the other six give. If those two sit far apart, read your max as a range between them instead of one exact number.
Rep counts in your percentage table
Below your result you'll see a list of lighter loads, and each one is a percentage of your max. Beside every load, you'll find roughly how many reps you could do. Epley supplies those counts as well, so the table always matches your main number. Each count is rounded, and none falls below 1 rep.
Show the steps for finding a rep count.
Divide 100 by the percentage, subtract 1, then multiply by 30. The result is rounded and stays at 1 rep or more.
Limits and rounding
- Every calculation uses exact numbers. Only displayed numbers are rounded.
- Pounds get rounded to the closest 1 lb. For kilograms, the closest half kilogram (0.5 kg) is used.
- Lift a weight just once and that weight becomes your max, so every formula returns the same number.
- Reps above 30 are treated as 30. A weight above 2,000 lb or above 1,000 kg is held at that cap.
- Change from pounds (lb) to kilograms (kg), or the other way, and the calculator converts the numbers for you.