RPE Calculator: Estimate Your 1RM From Reps and RPE
Enter weight, reps and RPE to estimate your 1RM with the standard RPE chart, then get the weight for any target reps and RPE. RPE and RIR explained.
RPE 8 ≈ 2 reps in reserve
RPE and RIR in plain words
RPE (rating of perceived exertion) is a score from 1 to 10 for how hard a set was. In lifting, the useful version ties each score to reps in reserve (RIR), the reps you had left when you stopped: RPE 10 means 0 reps left, RPE 9 means 1, RPE 8 means 2, and so on (Zourdos et al., 2016).
Rating each set this way lets you adjust the weight to how strong you are that day (Helms et al., 2016). The same review notes that a scale like this first appeared in the Reactive Training Systems manual in 2008, written for powerlifting.
How the calculator works
The calculator uses the RPE chart popularised by Mike Tuchscherer of Reactive Training Systems. Each cell is a percentage of your 1RM for a given number of reps at a given RPE. A few cells:
Reps | RPE 10 | RPE 9 | RPE 8 | RPE 7 |
|---|---|---|---|---|
1 | 100% | 95.5% | 92.2% | 89.2% |
3 | 92.2% | 89.2% | 86.3% | 83.7% |
5 | 86.3% | 83.7% | 81.1% | 78.6% |
8 | 78.6% | 76.2% | 73.9% | 70.7% |
Two formulas do the rest:
- Estimated 1RM = weight ÷ chart percentage
- Weight for a target = estimated 1RM × chart percentage for the target reps and RPE
A worked example
Made-up numbers: you bench 100 kg for 5 reps at RPE 8. The chart says 5 reps at RPE 8 is 81.1%, so your estimated 1RM is 100 ÷ 0.811 = about 123 kg. Next session calls for 3 reps at RPE 9, which is 89.2%: 123.3 × 0.892 = about 110 kg.
Notice the pattern: 5 reps at RPE 8 is the same percentage as 7 reps at RPE 10, because 5 reps plus 2 in reserve is 7.
Getting honest ratings
Judging reps in reserve takes practice. In the Zourdos study, experienced squatters rated a true max as harder than novices did, which suggests new lifters may underrate how close they are to failure. Film a few sets or train with a partner to check your calls.
The estimate is most reliable with low reps and RPE 7 to 10. The chart is an average, so your own percentages can differ. Don't take every set to RPE 10: Helms and colleagues advise caution with training to failure regularly. Warm up, keep your technique, and stop the set if something hurts.
Frequently asked questions
What is RPE in lifting?
A 1 to 10 score for how hard a set was. In the version used for lifting, each point below 10 means one rep left in the tank, so RPE 8 means you could have done 2 more.
What is the difference between RPE and RIR?
RIR counts the reps you had left; RPE turns that into a 1 to 10 score. RPE 10 is 0 RIR, RPE 9 is 1 RIR, RPE 8 is 2 RIR.
What RPE should I train at?
Most programs keep the bulk of their sets a few reps short of failure, often around RPE 7 to 9. Sets at RPE 10 are usually saved for tests or the last set of an exercise.
How accurate is an RPE chart?
It is an average across lifters, so treat the result as an estimate. It works best with low reps and honest ratings between RPE 7 and 10.
This is general information, not medical advice. Talk to a professional about your own situation.