Key Takeaways
- Your one rep max (1RM) is the heaviest weight you can lift once with good form. This page estimates it from a hard set of 1 to 10 reps using seven published equations[2], or from an RPE rating if you stopped before failure.
- The equations don't agree with each other. For 100 kg lifted 5 times they give 112.5 to 119 kg, so you get the average and the full range.
- Accuracy depends on the lift. In the one study that compared all seven on three lifts, they read low on the deadlift by 9 to 14%[2], and the overhead press has very little data behind it[9].
- Even at its best this is an estimate. The Australian Institute of Sport testing manual quotes about ±10% variability and says not to use predictions to record a 1RM[8].
What a 1RM Is, and How to Use This Page
Your one rep max is the most weight you can lift for a single rep with good form. If you can lift it twice, it was below your max.
A true max needs a proper warm-up, spotters and rest between attempts[8], so most people estimate it instead. Do a hard set to failure, enter the weight and the reps, and the page works out the rest.
The exercise picker changes the warnings only. The same seven equations run for every lift, because that is how they were published.
How the Estimate Works
Each equation turns the reps you did into a multiplier, and your 1RM is your weight times that multiplier. LeSuer and colleagues print all seven in their Table 1[2].
What happens when you press Calculate
- Each of the seven equations turns your reps into a multiplier.
- Your weight times each multiplier gives seven 1RM estimates.
- The page shows the lowest, the highest and the plain average of the seven.
- For 1 to 8 reps it also reads your set on the Helms RPE chart as a second opinion[5].
| Equation | Form | Multiplier at 5 reps | 1RM (kg) | Source |
|---|---|---|---|---|
| Epley | 1RM = w × (1 + 0.0333 × r) | × 1.167 | 116.7 | Epley, 1985 (workout chart) |
| Brzycki | 1RM = 100 × w ÷ (102.78 − 2.78 × r) | × 1.125 | 112.5 | Brzycki, 1993 |
| Lander | 1RM = 100 × w ÷ (101.3 − 2.67123 × r) | × 1.137 | 113.7 | Lander, 1985 |
| Lombardi | 1RM = w × r^0.1 | × 1.175 | 117.5 | Lombardi, 1989 |
| Mayhew | 1RM = 100 × w ÷ (52.2 + 41.9 × e^(−0.055 × r)) | × 1.190 | 119 | Mayhew et al., 1992 |
| O'Conner | 1RM = w × (1 + 0.025 × r) | × 1.125 | 112.5 | O'Conner et al., 1989 |
| Wathan | 1RM = 100 × w ÷ (48.8 + 53.8 × e^(−0.075 × r)) | × 1.166 | 116.6 | Wathan, 1994 |
w is the weight lifted and r is the reps to fatigue. The last two columns are arithmetic on each equation for 100 kg lifted 5 times.
LeSuer notes that some of these were first published as a percentage of 1RM and were turned into 1RM equations for the comparison[2]. The sources above come from his reference list. I checked Brzycki's equation against his own paper[1], but I only saw the other six as LeSuer printed them.
Worked example: 100 kg for 5 reps to failure
Epley: 100 × (1 + 0.0333 × 5) = 116.7 kg
Brzycki: 100 × 100 ÷ (102.78 − 2.78 × 5) = 112.5 kg
Lombardi: 100 × 5^0.1 = 117.5 kg
Brzycki's paper includes a worked table, and 225 lb for 10 reps comes out at about 300 lb[1]. The calculator's tests reproduce that.
He built the line from an unpublished observation, relayed in a 1981 review I haven't read, that 10 reps can be done at roughly 75% of a max, and says it is only valid for sets under about 10 reps.
The average is there because most people want one number. I haven't seen a study that tests the average, so treat the range as the real answer.
1RM Conversion Chart by Reps
Multiply your weight by the figure for your reps. The middle column is the average of the seven equations, and the last shows the lowest and highest.
| Reps | Average multiplier | Lowest to highest |
|---|---|---|
| 2 | × 1.061 | × 1.029 to × 1.114 |
| 3 | × 1.093 | × 1.059 to × 1.140 |
| 4 | × 1.124 | × 1.091 to × 1.165 |
| 5 | × 1.155 | × 1.125 to × 1.190 |
| 6 | × 1.185 | × 1.150 to × 1.215 |
| 7 | × 1.216 | × 1.175 to × 1.240 |
| 8 | × 1.247 | × 1.200 to × 1.277 |
| 9 | × 1.279 | × 1.225 to × 1.312 |
| 10 | × 1.310 | × 1.250 to × 1.347 |
1RM per 100 kg lifted to failure. Scale it to your own weight: 60 kg for 5 reps is 0.6 times the 100 kg result. A single rep is the 1RM itself.
The spread between the equations grows with the reps, which is one reason to use a heavier set when you can. For the reverse, switch to "I know my 1RM" and the page builds tables of loads from it.
How Accurate Is It?
Here is what each source actually looked at, so you can judge how far to trust a number:
| Source | What it found | Limit |
|---|---|---|
| LeSuer et al., 1997[2] | 67 untrained college students (40 men, 27 women) did a 1RM and a set of 10 or fewer reps to fatigue on each lift, though not everyone did every lift. All seven equations correlated highly with the measured 1RM (r above 0.95). Bench press: only Mayhew and Wathan did not differ significantly from the measured max, and the other five read low. Squat: only Wathan did not differ. Deadlift: all seven read low. | One study of untrained students. Bench press, squat and deadlift only. |
| Reynolds et al., 2006[3] | 70 people aged 18 to 69 did 1, 5, 10 and 20RM tests on the barbell bench press and a plate-loaded leg press. For predicting the 1RM, R² was 0.993 (bench) and 0.974 (leg press) from a 5RM, 0.976 and 0.933 from a 10RM, and 0.955 and 0.915 from a 20RM. The authors say to use no more than 10 reps in linear equations. | Bench press and leg press only. It fitted its own lines from measured data. |
| Mayhew et al., 2008[4] | 103 young women did bench press tests before and after 12 weeks of training. Prediction equations were more accurate when fewer than 10 reps to fatigue were used. | Young women, bench press only. |
| Varner et al., 2020[9] | 30 resistance-trained people (23 ± 3 years) did a 1RM, then a set to fatigue at 70% or 90% of it, on a press and the deadlift. At 70%, three of seven equations read significantly low on both lifts. At 90%, four equations read significantly high on the press and one on the deadlift. | A conference abstract. I couldn't open the full text, so I don't know which press or which equations. |
| Australian Institute of Sport, 2022[8] | Its testing manual says predictive equations shouldn't be used to calculate a 1RM. It notes they are influenced by the muscle group, the exercise and training level, with large variability (±10%) when submaximal reps are used. It says to record the weight and reps actually lifted. | A testing manual, not an experiment. It takes the ±10% from a 1992 study (Braith et al.) that I haven't read. |
- Heavy and short beats light and long. Brzycki says his equation is only valid for sets under about 10 reps[1]. LeSuer built on 10 or fewer[2], Reynolds says no more than 10[3], and Mayhew found better accuracy under 10[4]. So the calculator accepts 1 to 10 reps and warns at 8 or more.
- The set has to go to failure. The equations were built from reps to fatigue. If you stopped with reps left, the estimate reads low, which is why the page offers an RPE option.
- Judging failure is harder than it sounds. A review of 12 studies (414 people) found lifters under-predicted how many reps they had left by about 1 rep on average (95% interval 0.17 to 1.73), with large differences between studies. Predictions were better closer to failure and in sets of 12 reps or fewer[7]. The page makes no adjustment for this.
- Who was studied. College students and adults aged 18 to 69[2][3]. I found no data for teenagers or people over 70, so the calculator warns outside 18 to 69.
Squat, Bench Press and Deadlift
LeSuer's study is the only lift-by-lift comparison of all seven equations that I could check[2]. The students were untrained, so read these as the direction of the error more than a promise about your numbers.
- Bench press. Mayhew and Wathan did not differ significantly from the measured 1RM. The other five read low, by roughly 1 to 6%.
- Squat. Only Wathan did not differ significantly. The other six read low, by roughly 3 to 8%.
- Deadlift. All seven read low, by 9 to 14%. Varner's abstract also found low readings from sets at 70% of 1RM[9].
The bench and deadlift percentages are as printed in the paper's Table 3. The squat table prints pounds, so I worked those percentages out myself. The paper's own text quotes slightly wider ranges (0.8 to 6% and 2 to 8%), which seem to include the equations that did not differ.
I don't correct the numbers for any of this. I found no source for a correction factor, so the page shows a warning and leaves the equations as they are.
Overhead Press 1RM
The equations were not built on the press. LeSuer tested the bench press, squat and deadlift[2], and the only press study I found is the Varner abstract[9].
In that abstract, sets to failure at 70% of 1RM gave low estimates from three of the seven equations, and sets at 90% gave high estimates from four. I couldn't open the full text, so I can't tell you which equations or which press.
The Overhead Press 1RM Calculator is built for that lift. It covers the press evidence, a weight and reps chart, and push press, dumbbell and seated presses in more detail.
Percent of 1RM and the RPE Route
If your set stopped short of failure, the seven equations would read low. So the calculator has a second route: pick your RPE and it reads the percentage of 1RM from the Helms chart[5][6].
| Reps | RPE 10 | RPE 9.5 | RPE 9 | RPE 8.5 | RPE 8 | RPE 7.5 | RPE 7 |
|---|---|---|---|---|---|---|---|
| 1 | 100% | 97% | 95% | 93% | 91% | 89% | 87% |
| 2 | 95% | 93% | 91% | 89% | 87% | 86% | 85% |
| 3 | 91% | 89% | 87% | 86% | 85% | 84% | 83% |
| 4 | 87% | 86% | 85% | 84% | 83% | 82% | 81% |
| 5 | 85% | 84% | 83% | 82% | 81% | 80% | 79% |
| 6 | 83% | 82% | 81% | 80% | 79% | 77.5% | 76% |
| 7 | 81% | 80% | 79% | 77.5% | 76% | 74.5% | 73% |
| 8 | 79% | 77.5% | 76% | 74.5% | 73% | 71.5% | 70% |
Estimated % of 1RM by reps and RPE (Helms et al., 2016, Table 2).
Know what this chart is. Helms and colleagues built it from experienced squatters in one study[6], and only three cells come from measured sets: 1 rep at RPE 10, 1 rep at RPE 8 and 8 reps at RPE 7.
Every other value is the authors' estimate, and they say it shouldn't be treated as an exact conversion, especially for other lifts[5].
The chart stops at 8 reps, so the RPE route does too. To get your RPE from reps in reserve, use the RIR to RPE Calculator.
If You Test a True 1RM
The Australian Institute of Sport testing manual, version 2.0 (effective July 2022), is the most detailed protocol I found[8]. It is written for athlete testing, and I read its bench press section in detail. Its warm-up for a bench press 1RM looks like this:
| Set | % of predicted 1RM | Reps | Rest after |
|---|---|---|---|
| 1 | 40 to 60% | 10 or fewer | 2+ min |
| 2 | 60 to 70% | 5 or fewer | 2+ min |
| 3 | 70 to 80% | 5 or fewer | 2+ min |
| 4 | 90% | 1 to 3 | 2 to 5 min |
Bench press 1RM warm-up from the AIS manual. Weights are a percentage of the 1RM you expect to lift.
- Attempts. If a lift goes well, add weight (the manual suggests steps like 95%, 97.5%, 100% and above of the predicted load) until you reach your max. It aims for the result within 4 trials, not counting the warm-up, with 2 to 5 minutes between attempts.
- Safety. It recommends two experienced spotters for maximal bench press efforts, and ends the test once a technical violation is seen.
- Warm-up loads. It says to work them out from recent training data or an earlier result. The estimate from this page can stand in for that, with the error described above.
- Readiness. It suggests no severe training fatigue in the 72 hours before, and at least 6 sessions of practising the lift beforehand.
The same manual has squat and deadlift protocols, which I haven't summarised here. It has none for the overhead press.
Getting a Better Estimate
- Use a heavy set taken to failure, and count only reps you would accept in a max. In LeSuer's study the bar had to touch the chest and pause on the bench press, the thighs had to reach parallel on the squat, and the lifter had to stand fully erect without bouncing on the deadlift[2].
- Read the range, not only the average. A wide range means less reason to trust any single number.
- Check the warning for your lift. The deadlift and overhead press carry the biggest caveats.
- Treat the result as a starting load, not a verdict. The AIS manual says to log the weight and reps you actually lifted[8].
- For a single rep-range version, see the 3 Rep Max Calculator or the 5 Rep Max Calculator. To turn reps and effort into a load, use the RPE Calculator.
What This Page Leaves Out
I left these out because I couldn't trace them to a source I could open:
- Strength standards and bodyweight ratings. A fixed table ignores bodyweight, sex and training age.
- A "best" equation for each rep count. The studies above don't name one.
- Percentages for strength, size or endurance goals. I found no study I could cite for a single set of ranges.
- Exercise variations, periodisation, mobility and injury advice. None tied to a source I could open.
- Leg press. It has its own page elsewhere on the site, and I haven't rebuilt it here.
Still unverified: the original publications for Epley, Lander, Lombardi, Mayhew, O'Conner and Wathan, and the 1992 study behind the AIS ±10%.
I also haven't read the large review of reps at a given percentage of 1RM, so I don't quote it. The AIS manual is the latest version I could find (2.0, July 2022).
Frequently Asked Questions
Sources & References
- Strength testing: predicting a one-rep max from reps-to-fatigue. Brzycki M. Journal of Physical Education, Recreation & Dance 64(1):88-90 (1993)
- The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. Journal of Strength and Conditioning Research 11(4):211-213 (1997)
- Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. Reynolds JM, Gordon TJ, Robergs RA. Journal of Strength and Conditioning Research 20(3):584-592 (2006)
- Accuracy of prediction equations for determining one repetition maximum bench press in women before and after resistance training. Mayhew JL, Johnson BD, LaMonte MJ, Lauber D, Kemmler W. Journal of Strength and Conditioning Research 22(5):1570-1577 (2008)
- Application of the repetitions in reserve-based rating of perceived exertion scale for resistance training. Helms ER, Cronin J, Storey A, Zourdos MC. Strength and Conditioning Journal 38(4):42-49 (2016)
- Novel resistance training-specific rating of perceived exertion scale measuring repetitions in reserve. Zourdos MC, Klemp A, Dolan C, Quiles JM, Schau KA, Jo E, Helms E, Esgro B, Duncan S, Garcia Merino S, Blanco R. Journal of Strength and Conditioning Research 30(1):267-275 (2016)
- Accuracy in predicting repetitions to task failure in resistance exercise: a scoping review and exploratory meta-analysis. Halperin I, Malleron T, Har-Nir I, Androulakis-Korakakis P, Wolf M, Fisher J, Steele J. Sports Medicine 52(2):377-390 (2022)
- National Protocols for the Assessment of Strength and Power, Version 2.0 (effective July 2022). Australian Institute of Sport and the National Institute Network. Australian Sports Commission (2022)
- The accuracy of prediction equations for estimating 1RM in the press and the deadlift (conference abstract). Varner W, Boring J, Beck LL, Beck M, Fahs CA. Medicine & Science in Sports & Exercise 52(7S):46-47 (conference abstract). Abstract only; full text not opened (2020)
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Disclaimer: This tool is for informational and personal journaling purposes only. Results are estimates based on published formulas and may vary based on individual factors such as genetics, training history, and measurement technique.