One Rep Max Calculator
Enter the weight you lifted and how many clean reps you got to estimate your one rep max (1RM) with the Epley and Brzycki formulas, plus a table of working weights from 50% to 100% of it. Works for sets of 1–10 reps; it's an estimate, not a tested max.
Weight unit
Formula for the main result
Working weights by % of 1RM
| % of 1RM | Weight |
|---|---|
| 100% | 116.7 lb |
| 95% | 110.8 lb |
| 90% | 105.0 lb |
| 85% | 99.2 lb |
| 80% | 93.3 lb |
| 75% | 87.5 lb |
| 70% | 81.7 lb |
| 65% | 75.8 lb |
| 60% | 70.0 lb |
| 55% | 64.2 lb |
| 50% | 58.3 lb |
Getting a useful estimate
- Use a set you actually took to failure, or very close to it, with good form. If you stopped with three reps left in the tank, the formulas will underestimate your max.
- Heavier sets give better estimates. A 3–5 rep set predicts your max more reliably than a set of 10, and the formulas aren't trustworthy above 10 reps, which is why the calculator stops there.
- The formulas were mostly built on the bench press. For squats, deadlifts and machine lifts the estimate can be off in either direction, so treat it as a starting point.
- Don't test or chase a heavy single alone. Lift with a spotter or safety bars, and if you have an injury or a health condition, ask a doctor or a qualified coach first.
An estimate, not a tested max. Your real 1RM can differ by 10% or more.
How this is calculated
Both formulas turn a set of several reps into an estimated single-rep max. Epley (1985) multiplies the weight by 1 + reps ÷ 30, so each extra rep adds about 3.3% of the weight. Brzycki (1993) multiplies it by 36 ÷ (37 − reps), which grows a little more slowly at low reps. The two agree exactly at 10 reps; below that, Epley gives a slightly higher number. The main result uses Epley by default, and Brzycki is shown next to it. A single rep is your max by definition, so for 1 rep both return the weight itself. Neither formula depends on units, so your 1RM comes out in whatever unit you entered, kilograms or pounds. The percentage table then multiplies the estimate by 95%, 90% and so on down to 50%. The equations come from coaching charts and practitioner articles. Later studies found them reasonable up to about 10 reps, but more accurate for some lifts than for others.
Common questions
Which formula should I use, Epley or Brzycki?
Neither is best for every lift. Studies comparing them found that accuracy depends on the exercise and on the lifter, and the two give the same answer at 10 reps. Below 10 reps Brzycki is the more conservative of the two, so it's the safer pick for planning working weights. The calculator shows both so you can see how far apart they are.
How accurate is an estimated 1RM?
It's a ballpark figure. For trained lifters doing heavy sets of a few reps it's usually close. But your real max can differ by 10% or more, especially if you're a beginner, if the set was high-rep, or for lifts like the deadlift or leg press. Use it to plan training loads, not as a record.
Why can't I enter more than 10 reps?
Because the formulas stop being reliable there. Above about 10 reps, endurance matters more than maximal strength, and different formulas start giving very different answers for the same set. If you want an estimate, do a heavier set that you can only manage for 10 reps or fewer.
Part of Sports & Fitness Calculators