One Rep Max Calculator
Estimate your one-rep max from a submaximal set with the Epley, Brzycki, Lombardi and O’Conner equations.
Result
Enter weight lifted and repetitions completed to see the result.
https://calcgallery.com/fitness-training/one-rep-max-calculator/
How to use the One Rep Max Calculator
- Enter the weight you lifted and the number of clean repetitions you completed.
- Use a set taken close to failure. The equations assume that.
- Read the four estimates, not just the average.
- Check the spread. Above eight repetitions it grows quickly.
How it is calculated
Four published equations, each taking the weight lifted and the repetitions completed:
| Formula | Year | Equation |
|---|---|---|
| Epley | 1985 | w × (1 + r ÷ 30) |
| Brzycki | 1993 | w × 36 ÷ (37 − r) |
| Lombardi | 1989 | w × r^0.10 |
| O’Conner | 1989 | w × (1 + 0.025 × r) |
All of them assume the set was taken close to failure with consistent technique. A set of eight that could have been twelve is not the input these equations are describing.
At a single repetition Brzycki and Lombardi return the weight itself exactly, which is the cheapest possible check that none of the four has been mistyped. Epley and O’Conner return slightly more, because their linear forms do not pass through the origin at r = 1.
Where they stop agreeing
This is the part worth looking at, and it is why four numbers are shown instead of one.
| Reps | Epley | Brzycki | Lombardi | O’Conner | Spread |
|---|---|---|---|---|---|
| 1 | 103 | 100 | 100 | 103 | 3 kg |
| 5 | 117 | 113 | 117 | 113 | 5 kg |
| 10 | 133 | 133 | 126 | 125 | 8 kg |
| 20 | 167 | 212 | 135 | 150 | 77 kg |
From a 100 kilogram lift.
Through about eight repetitions the four sit within a few kilograms of each other and the average is a reasonable summary. Past that they fan out fast, because each is extrapolating a different curve well beyond where it was fitted. By twenty repetitions the estimates span seventy-seven kilograms, and an average of four numbers that far apart is not more informative than any one of them.
The practical conclusion is to estimate from sets of three to six, where the equations agree, and treat anything derived from a high-repetition set as a rough indication.
Practical tips
Estimate from low-repetition sets. Three to six is where the four equations converge and where the estimate is worth having.
Take the set close to failure. These equations describe what happens when repetitions run out, not when you decide to stop.
Track the same lift with the same formula. The change over months is far more useful than the absolute number, and switching formulas adds noise that has nothing to do with strength.
Watch the spread, not just the average. It is the page’s own statement of how much confidence the estimate deserves.
Treat the number as a planning tool. It is useful for choosing training loads as a percentage. It is not a claim about what you could lift today.
With your numbers
- Epley multiplies 225 lb by 1 + 5 ÷ 30, giving 262.5 lb
- Brzycki 253.1 lb, Lombardi 264.3 lb and O’Conner 253.1 lb span 11.2 lb
- Averaging the four gives 258.3 lb
Quick reference
An estimate from a submaximal set, assuming it was taken close to failure with consistent technique. Above about eight reps the four equations diverge sharply.
| Example | Estimated one-rep max, average of four |
|---|---|
| 135 lb for 5 | 155 lb |
| 185 lb for 8 | 228.4 lb |
| 225 lb for 5 | 258.3 lb |
| 275 lb for 3 | 299.1 lb |
| 60 kg for 10 | 77.6 kg |
| 100 kg for 1 | 101.5 kg |
| 100 kg for 8 | 123.5 kg |
| 100 kg for 20 | 165.8 kg |
Common questions about the One Rep Max Calculator
- Which formula is most accurate?
- In the range they were built for, at low repetitions, all four agree closely and the choice barely matters. Above about eight they diverge, and there is no basis on this page for saying which is right, because that depends on the lift, the lifter and how the set was performed. Brzycki is known to run high at high repetitions and Lombardi low; the honest answer is to test in a range where they agree.
- Why is my estimate higher than what I can actually lift?
- Three common reasons. The set was not truly close to failure, so the repetitions understate how hard it was. The estimate came from a high-repetition set, where the equations extrapolate badly. Or the lift is one where a single maximal attempt is limited by technique, balance or confidence rather than by the muscle, which the equations do not model.
- Does it work for every lift?
- It is least reliable on small-muscle and technically demanding lifts. The equations were developed mainly around large compound movements, where repetition performance tracks maximal strength reasonably well. On an isolation exercise, or a lift where stability is the limiting factor, the relationship between a set of eight and a single maximum is much weaker.
- Why does the page cap repetitions at thirty?
- Partly arithmetic and partly honesty. Brzycki divides by 37 minus the repetition count, which reaches zero at thirty-seven and returns a negative number beyond it. Well before that the estimates stop meaning anything: at thirty repetitions Brzycki predicts 514 kilograms from a 100 kilogram lift, which is not an estimate of anything.
- Should I test my actual one-rep max instead?
- That is a training decision rather than an arithmetic one. A true maximal attempt carries more risk and requires a proper warm-up, a spotter and a plan, and it costs recovery. Estimating from a set of three to five gives a usable number with none of that. Whichever you do, the estimate is most useful as something to compare against itself over time.