How the bench PR calculator works out your max
Your one-rep max (1RM) means the heaviest weight you could bench press for a single rep, and that's what the calculator estimates. It uses a lighter weight that you lifted several times in a row as its starting point. People call every one of those lifts a rep. The main result is worked out with the Epley formula. Six other well-known formulas appear here too, so you can compare their answers.
The Epley formula
Epley follows a simple rule: lift a weight more times and you could lift a heavier weight for one rep. Your estimate goes up a little with each extra rep. When you bench press 225 pounds (lb) for 10 reps, Epley puts your max at about 300 lb.
The main result comes from it, since it is simple to check by hand and most bench calculators give the same value. Brzycki, a second formula, gives an identical result at 10 reps.
Look at the Epley math.
In short, Epley gives max = (1 + reps ÷ 30) × weight. With 225 lb and 10 reps, that gives 300 lb.
The seven bench press 1RM formulas
Every formula is named for the researcher who published it. The same two numbers feed every formula: the weight you lifted, and the number of reps you did. Each handles those numbers differently, so each returns a slightly different answer. For 225 lb lifted 10 times, the table lists what each formula gives.
| 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 |
Check the math behind each formula
In the table, w stands for the weight you lifted and r for the number of reps.
| 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) |
Every formula and the study that first published it are listed on the one-rep max page on Wikipedia.
How accurate are the formulas for bench press?
In 1997, researchers tested all seven formulas against the heaviest single lift each person could really manage. The lifts they tested were the bench press plus two other big ones, the squat and the deadlift. Among the 67 people studied, all were college students new to lifting, and no one performed more than 10 reps in a row.
| 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 matched the real maxes most closely. The remaining five landed slightly below the real maxes. From: LeSuer and colleagues' 1997 research.
Every formula has its limits. Under your result, you can see the lowest and highest answers the other six formulas give. When those two numbers sit far apart, treat your max as falling somewhere between them rather than one exact figure.
How the numbers are rounded
- The calculator uses exact numbers, and it rounds them only when it shows them to you.
- For pounds, we round to the nearest 1 lb, and for kilograms the nearest half kilogram (0.5 kg).
- Lift a weight only once and that weight is your max, so all the formulas return the same number.
- The calculator treats anything over 30 reps as 30. The calculator caps weights over 2,000 lb or 1,000 kg at that limit.
- Whenever you move from pounds (lb) to kilograms (kg) or back, the calculator converts it for you.
Where the reps in the percentage table come from
A table of lighter weights sits below your result, and each weight is a percentage of your max. For every weight listed, you can see roughly how many reps you'd be able to do. The same Epley formula produces those numbers, so the table always lines up with your main result. Each count gets rounded, and it never shows fewer than 1 rep.
See how the rep counts are worked out.
The tool divides 100 by the percentage, subtracts 1, then multiplies by 30. The answer gets rounded, and it never shows fewer than 1 rep.