Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How RPE-Based Training Loads Are Calculated
In lifting, RPE (rate of perceived exertion) is a 1 to 10 rating of how hard a set was, based on how many more reps you could have done. Those leftover reps are called reps in reserve (RIR). Reps done plus reps left tell you roughly which rep max you lifted, and from there the calculator estimates your 1RM and the load for any target set.
What RPE Measures
RPE measures how close a set came to failure, the point where you could not do another rep with good form. It is not a rating of overall tiredness. The lifting scale ties each number to reps left¹:
RPE | Reps left (RIR) | Meaning |
10 | 0 | Maximum effort |
9.5 | 0 to 1 | No more reps, but you could add a little weight |
9 | 1 | 1 rep left |
8.5 | 1 to 2 | Maybe 2 reps left |
8 | 2 | 2 reps left |
7.5 | 2 to 3 | Maybe 3 reps left |
7 | 3 | 3 reps left |
5 to 6 | 4 to 6 | Several reps left |
Ratings of 3 to 4 mean light effort, and 1 to 2 mean little to no effort¹. This calculator accepts RPE 6 to 10.
The Formula
Reps in reserve (RIR) = 10 - RPE
Reps to failure = reps done + RIR
Estimated 1RM = weight x (1 + reps to failure / 30)
Percent of 1RM = 30 / (30 + reps to failure) x 100
Target load = estimated 1RM x target percent of 1RM
Adding reps left to reps done follows Helms and colleagues, who note that 6 reps with none left and 3 reps with 3 left use about the same load². The 1RM step is Epley's rep max equation³, the same one our One Rep Max Calculator uses. Unlike that calculator, this one counts a single at RPE 10 as 100% of your 1RM, because Epley's equation is meant for more than one rep³.
How This Calculator Computes Your Result
Pick lb or kg, enter the weight and reps (1 to 12), and choose the set's RPE in half steps from 6 to 10 (9.5 counts as half a rep left). The tool shows your estimated 1RM to one decimal in both units, plus the percent of it your set was.
Add target reps and a target RPE to plan a set. The tool multiplies your estimated 1RM by the target percent and rounds to the nearest 5 lb or 2.5 kg (a pair of 2.5 lb or 1.25 kg plates), which you can change. A value exactly halfway rounds down, and the suggestion never goes above your estimated 1RM. A table under the result shows loads for every rep count and RPE.
For example, 225 lb for 5 reps at RPE 8 was roughly a 7-rep max, which gives an estimated 1RM of 277.5 lb. For 8 reps at RPE 7, the suggested load is 205 lb (exact 203.0 lb).
What Your Result Means
Your estimated 1RM is the most you could likely lift once, based on this one set. The percent shows how heavy the set was compared with that max. This chart shows the percent of 1RM the calculator uses (half steps fall between the columns):
Reps | RPE 10 | RPE 9 | RPE 8 | RPE 7 | RPE 6 |
1 | 100.0% | 93.8% | 90.9% | 88.2% | 85.7% |
2 | 93.8% | 90.9% | 88.2% | 85.7% | 83.3% |
3 | 90.9% | 88.2% | 85.7% | 83.3% | 81.1% |
4 | 88.2% | 85.7% | 83.3% | 81.1% | 78.9% |
5 | 85.7% | 83.3% | 81.1% | 78.9% | 76.9% |
6 | 83.3% | 81.1% | 78.9% | 76.9% | 75.0% |
7 | 81.1% | 78.9% | 76.9% | 75.0% | 73.2% |
8 | 78.9% | 76.9% | 75.0% | 73.2% | 71.4% |
9 | 76.9% | 75.0% | 73.2% | 71.4% | 69.8% |
10 | 75.0% | 73.2% | 71.4% | 69.8% | 68.2% |
11 | 73.2% | 71.4% | 69.8% | 68.2% | 66.7% |
12 | 71.4% | 69.8% | 68.2% | 66.7% | 65.2% |
This kind of scale was first set out for powerlifting in Mike Tuchscherer's Reactive Training Systems manual in 2008². Treat any RPE chart as a guide. Helms and colleagues, who published a similar chart, warn that it is not an exact conversion because people differ².
How Accurate Are RPE Ratings?
A 2022 meta-analysis of 12 studies with 414 people found that people guessed about 1 rep short on average, so they could do about one more rep than they thought⁴. If you underrate your reps left, your estimated 1RM comes out a little low.
Guesses were more accurate closer to failure and much less accurate in sets with more than 12 reps to failure⁴. Training experience made little difference in that analysis⁴, though one study found that experienced squatters rated a true max at 9.8 on average and novices at 9.0¹. A heavier set close to failure tends to give a better estimate than a light set with many reps left⁴.
How Lifters Use RPE to Adjust Load
Setting the weight by RPE is a form of autoregulation: the load follows how strong you are that day instead of a fixed number from an old max. In an 8-week study of 21 trained men, one group lifted set percentages of 1RM and the other chose loads to hit target RPEs⁵. The RPE group changed the load by 2% for every half point a set landed outside its target range⁵. Gains were slightly larger with RPE (squat 17.1 vs 13.9 kg, bench press 10.7 vs 9.6 kg), but the differences were not statistically significant⁵.
The same RPE can mean different loads on different lifts. A review of 269 studies found that people do more reps in the leg press than the bench press at the same percent of 1RM, and that rep counts vary less at heavier loads⁶. In an older study of untrained students, all seven rep max equations tested underestimated the deadlift max⁷. Your estimate is most useful when you compare it with earlier sets of the same lift.
RPE Chart: Percent of 1RM by Reps and RPE
The percent of your estimated 1RM a set represents, including the half steps. Pick your reps and RPE to find yours.
- Under 70%
- 70 to 79.9%
- 80 to 89.9%
- 90% and over
| Reps | RPE 10 | RPE 9.5 | RPE 9 | RPE 8.5 | RPE 8 | RPE 7.5 | RPE 7 | RPE 6.5 | RPE 6 |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 100.0 | 95.2 | 93.8 | 92.3 | 90.9 | 89.6 | 88.2 | 87.0 | 85.7 |
| 2 | 93.8 | 92.3 | 90.9 | 89.6 | 88.2 | 87.0 | 85.7 | 84.5 | 83.3 |
| 3 | 90.9 | 89.6 | 88.2 | 87.0 | 85.7 | 84.5 | 83.3 | 82.2 | 81.1 |
| 4 | 88.2 | 87.0 | 85.7 | 84.5 | 83.3 | 82.2 | 81.1 | 80.0 | 78.9 |
| 5 | 85.7 | 84.5 | 83.3 | 82.2 | 81.1 | 80.0 | 78.9 | 77.9 | 76.9 |
| 6 | 83.3 | 82.2 | 81.1 | 80.0 | 78.9 | 77.9 | 76.9 | 75.9 | 75.0 |
| 7 | 81.1 | 80.0 | 78.9 | 77.9 | 76.9 | 75.9 | 75.0 | 74.1 | 73.2 |
| 8 | 78.9 | 77.9 | 76.9 | 75.9 | 75.0 | 74.1 | 73.2 | 72.3 | 71.4 |
| 9 | 76.9 | 75.9 | 75.0 | 74.1 | 73.2 | 72.3 | 71.4 | 70.6 | 69.8 |
| 10 | 75.0 | 74.1 | 73.2 | 72.3 | 71.4 | 70.6 | 69.8 | 69.0 | 68.2 |
| 11 | 73.2 | 72.3 | 71.4 | 70.6 | 69.8 | 69.0 | 68.2 | 67.4 | 66.7 |
| 12 | 71.4 | 70.6 | 69.8 | 69.0 | 68.2 | 67.4 | 66.7 | 65.9 | 65.2 |
Use the arrow keys to move between cells.
A Note on Accuracy
This calculator turns one rating into an estimate, so it is only as good as your RPE. Misjudging reps left by one rep changes the estimated 1RM by about 2 to 3% (more for a single at RPE 10). The math is a general rep max equation, not one fitted to you or to a given lift. Use the result to plan training loads, not as a max to attempt.
Frequently Asked Questions
What does RPE 8 mean in lifting?
RPE 8 means you finished the set with about 2 reps left before failure¹. For example, 5 reps at RPE 8 is roughly a 7-rep max, about 81% of your 1RM by this calculator's formula.
How do you calculate 1RM from RPE?
Add the reps you did to the reps you had left (10 minus RPE), then put that total into Epley's equation, weight x (1 + total / 30)² ³. For 225 lb x 5 at RPE 8, that gives 277.5 lb.
Is lifting RPE the same as the Borg RPE scale?
No. The Borg scale rates overall physical effort, such as during cardio, from 6 (no exertion) to 20 (maximal exertion)⁸ ⁹. Lifting RPE runs from 1 to 10 and is tied to the reps left in a set¹.
How accurate is an RPE calculator?
It is a useful estimate, not an exact one. Lifters misjudge reps left by about 1 rep on average⁴, which shifts the result by a few percent, and the error grows in long sets far from failure.
Sources
Novel Resistance Training-Specific RPE Scale Measuring Repetitions in Reserve, Zourdos et al., 2016
Application of the RIR-Based RPE Scale for Resistance Training, Helms et al., 2016
One-Repetition Maximum, Wikipedia
Accuracy in Predicting Repetitions to Task Failure, Halperin et al., 2022
RPE vs. Percentage 1RM Loading in Periodized Programs, Helms et al., 2018
Maximal Number of Repetitions at Percentages of 1RM, Nuzzo et al., 2024
The Accuracy of Prediction Equations for Estimating 1-RM Performance, LeSuer et al., 1997
Psychophysical Bases of Perceived Exertion, Borg, 1982
Rated Perceived Exertion (RPE) Scale, Cleveland Clinic, 2023