Key Takeaways
- RPE here is a count of reps you had left. The chart turns reps and RPE into a percentage of your 1RM: 5 reps at RPE 8 is 81%, so 100 kg for 5 at RPE 8 points to a max of about 123.5 kg[1].
- The chart covers 1 to 8 reps and RPE 7 to 10. Only three loads were actually tested, and every other value is an estimate[1].
- It was built from trained squatters. The authors say it may differ for machine, single-joint and upper-body exercises, and should not be used as an absolute conversion[1].
- Your RPE is the weakest input. On average, lifters guessed they had about 1 rep fewer left than they really did, so an RPE-based 1RM can read low[3].
How RPE Becomes a Percentage of 1RM
RPE on this scale is a count of reps left in the tank, not a general feeling of effort. RPE 10 means none, RPE 9 means 1 and RPE 8 means 2[2]. If you think in reps in reserve, the RIR to RPE calculator converts between the two.
| RPE | Reps in reserve | What it means |
|---|---|---|
| 10 | 0 | Maximum effort |
| 9 | 1 | 1 repetition remaining |
| 8 | 2 | 2 repetitions remaining |
| 7 | 3 | 3 repetitions remaining |
Whole-number rows of the reps in reserve scale (Helms et al. 2016, Table 1). Half points sit in between.
The chart then gives a percentage of 1RM for each pair of reps and RPE. To estimate your max, divide the weight you lifted by that percentage. To plan a load, multiply your 1RM by it.
Estimated 1RM = weight / (percent / 100)
Load = 1RM x percent / 100
Worked example
- The set
- 100 kg for 5 reps at RPE 8
- From the chart
- 81% of 1RM
- Estimated 1RM
- 100 / 0.81 = 123.5 kg
- Next week
- 3 reps at RPE 8 is 85%, so 123.5 x 0.85 = 104.9 kg. In 2.5 kg steps that is 105 kg.
The calculator rounds to the step you pick, 2.5 kg by default, so for the first line it shows 122.5 kg rather than 123.5 kg. Choose 0.5 kg if you want it closer to the exact figure. Once you have the load, the warm-up calculator can build the sets leading up to it.
- Pick RPE to %1RM, %1RM to RPE, or Estimate my 1RM.
- Choose your reps (1 to 8) and your RPE (7 to 10), or enter the percentage you were given.
- Add your 1RM or the weight you lifted, if the answer should be in kilograms or pounds.
- Press Convert and read the answer, then check the highlighted cell in the chart.
RPE to Percentage of 1RM Chart
Find your reps down the left, then read across to your RPE. The whole-number RPEs are in bold, with the half points between them.
| Reps | RPE 10 | RPE 9.5 | RPE 9 | RPE 8.5 | RPE 8 | RPE 7.5 | RPE 7 |
|---|---|---|---|---|---|---|---|
| 1 | 100% (a load the study tested) | 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% (a load the study tested) |
* Matches a load the study tested: a single at 100% and 8 reps at 70%. Every other cell is an estimate.
The chart is built from the average RPE that experienced squatters reported for a single at 100% of 1RM, a single at 90% and a set of 8 at 70%[1]. The 90% single falls between RPE 8 (91%) and RPE 7.5 (89%), so no cell is marked for it.
Even at the tested 8 reps at 70%, lifters differed. The standard deviation was 1.2, so roughly two thirds of lifters may report 2 to 4 reps left, and some may report 1 or 5[1].
Whole-number RPEs line up along diagonals. So 5 reps at RPE 8 and 7 reps at RPE 10 both sit at 81%. The paper shows the same at 83%: 6 reps at RPE 10, 5 at RPE 9, 4 at RPE 8 or 3 at RPE 7[1].
RPE Estimates Versus Rep-Based 1RM Formulas
Epley, Brzycki and the other rep-based equations assume the set went to failure. The RPE chart does not, so it also works for a set you stopped early.
At RPE 10 the two approaches land in the same area. For 5 reps to failure the chart says 85%, and the seven equations in LeSuer and colleagues give 84% to 88.9%[4].
| Source | % of 1RM at 5 reps |
|---|---|
| Helms chart, RPE 10 | 85% |
| Epley | 85.7% |
| Brzycki | 88.9% |
| Lander | 87.9% |
| Lombardi | 85.1% |
| Mayhew | 84% |
| O'Conner | 88.9% |
| Wathan | 85.8% |
Share of 1RM at 5 reps to failure. For each equation this is 100 divided by its multiplier for 5 reps.
If you really did take a set to failure, the 3RM, 5RM and 1RM calculators show the full spread across the equations. For a set you stopped short of failure, the RPE chart is the better fit.
How Accurate Is RPE to 1RM?
No source here gives an error range for an RPE-based 1RM, so the calculator shows none. What the research does show is that the rating you feed in is the shaky part.
0.95 reps
Average amount lifters underpredicted the reps they had left (95% CI 0.17 to 1.73), across 12 studies and 414 people.[3]
SD 1.2
Standard deviation of the RPE scores for 8 reps at 70% of 1RM, one of the three tested points behind the chart.[1]
The studies disagreed a lot, so treat 0.95 as an average and not a promise. Predictions were slightly better closer to failure, with heavier loads and in later sets[3]. So an RPE 8 on a heavy set of 3 to 5 is a more dependable input than one from a long, light set.
Training age is less clear cut. The pooled analysis found no clear effect of training status on accuracy[3], yet in the study behind the scale, experienced squatters rated a 1RM attempt higher than novices, who had under a year of squatting[2]. The chart came from trained lifters, so it fits them best.
What this means for you
Squat, Bench Press and Deadlift
The chart was built from barbell back squats. Helms and colleagues warn that it may change with machine, single-joint or upper-body exercises[1]. Nothing in the paper is specific to the bench press or the deadlift.
One related finding is about your rating, not the chart. In the pooled analysis, accuracy at predicting reps left did not clearly differ between upper-body and lower-body exercises[3]. That says nothing about whether the chart percentages fit each lift.
So the calculator applies the same percentages to every lift and does not adjust them by exercise. Treat the result as a starting point and compare it with how your own sets go. For a bench press specifically, the bench press 1RM calculator is built around that lift.
What This Calculator Does Not Cover
- 9 or more reps, and RPE below 7. The paper has no cells for them, and stretching the chart with a formula would be a guess.
- Per-exercise factors. Some calculators scale the percentages by lift, but no source here backs any such factor.
- Charts that run to 12 reps and RPE 6. These circulate online, often credited to Mike Tuchscherer, whose 2008 Reactive Training Systems manual is where Helms and colleagues say an RIR-based scale first appeared[1]. Their tables are not published in the research cited here, so they are not used.
Frequently Asked Questions
Sources & References
- 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)
- 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)
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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.