Health & Fitness
One Rep Max Calculator
Enter a weight and reps to estimate your one-rep max with four standard formulas, plus a full training-percentage table.
Training percentages
| % of 1RM | Reps | Weight |
|---|---|---|
| 100% | 1 | — |
| 95% | 2 | — |
| 93% | 3 | — |
| 90% | 4 | — |
| 87% | 5 | — |
| 85% | 6 | — |
| 83% | 7 | — |
| 80% | 8 | — |
| 77% | 9 | — |
| 75% | 10 | — |
| 70% | 12 | — |
| 65% | 15 | — |
How it works
Behind the numbers
Testing a true one-rep max is risky and tiring, so lifters estimate it from a lighter set taken close to failure. You enter the weight on the bar and how many clean reps you managed, and the calculator runs four published formulas on that pair: Epley, Brzycki, Lombardi, and O'Conner. Each one models the weight-to-reps curve a little differently, which is why showing all four beats trusting any single one.
The headline number is the average of the four, which smooths out each formula's bias. Brzycki runs a touch conservative at low reps, Lombardi a touch generous; averaging keeps either extreme from setting your training weights. All four were built from rep ranges under about ten, so treat anything estimated from a 15-rep set as a rough guess rather than a prescription.
Below the formulas sits a training table: standard percentages of your 1RM with the rep counts coaches pair them with, from 100 percent for singles down to 65 percent for sets of fifteen. Pick a percentage, read the weight, and you have a starting load for the session. Everything runs in your browser; nothing you type leaves the page.
FAQ
Questions, answered
What is a one-rep max?
Your one-rep max, or 1RM, is the heaviest weight you can lift once with good form. It is the reference point coaches use to set training loads: instead of guessing, a program says lift 80 percent of your 1RM and you know the exact weight. Because maxing out is risky, most lifters estimate it from a submaximal set, which is what this calculator does.
Which 1RM formula is most accurate?
No single formula wins everywhere, which is why this page shows four. Epley is the most cited in coaching literature, Brzycki tends to run conservative, Lombardi generous, and O'Conner sits between them. Studies comparing them find the differences are a few percent for sets under ten reps. Averaging the four, as the headline number does, is the most defensible single estimate.
How do I use the percentage table?
Read across from the percentage to the weight: that is your working load for the rep count in the middle column. A common pattern is 3 to 5 sets of 5 at 85 percent, or 3 sets of 10 at 75 percent. If the last set feels easy across two sessions, add the smallest plate and retest your estimate every couple of months.
Why do the four formulas give different numbers?
Each formula fits a different curve through observed lifting data. Epley assumes each extra rep costs one-thirtieth of your max, Brzycki uses a steeper curve, Lombardi an exponential one, and O'Conner a gentler slope. Real lifters also differ: endurance-type lifters beat the formulas at high reps, explosive lifters beat them at low reps. A spread of a few kilos between formulas is normal, not an error.