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How to Use the RPE Calculator
RPE (Rating of Perceived Exertion) adapts the Borg scale from exercise physiology for powerlifting and strength training. It rates how much you had left in the tank on a given set, on a 10-point scale, and forms the basis of autoregulation — adjusting your training load to how you feel each day.
How to use this tool
Right after a set, enter the weight and reps you performed along with the RPE for that set. The RIR (reps in reserve) implied by your RPE is added to your rep count to get an "effective rep max", which is then run through the same Epley formula used on the 1RM Calculator. Unlike a standard 1RM calculator, which assumes the set was taken to failure, this tool also works for sets stopped short of failure.
Reading your results
"%1RM" shows what percentage of your estimated 1RM today's weight represents. A common approach is to train most sets around RPE 8-9 and occasionally push to RPE 9.5-10 to test your limits. The Interval Calculator can help with rest times between sets.
Getting better at RPE
It's normal to be inaccurate at first. Practise estimating reps in reserve after every set, then compare against days you actually trained to failure to calibrate your sense over several weeks to months. A good rule of thumb is to gauge it against the point where your form starts to break down.
How RPE maps to RIR
In resistance training, RPE is normally paired with RIR — reps in reserve. RPE 10 means none left, RPE 9 means one, RPE 8 two and RPE 7 three. Answering "how many more could I have done?" is far more repeatable than rating exertion on an abstract ten-point scale, so RIR is the better thing to write in a log.
What autoregulation buys you
A programme that prescribes fixed weights cannot know how you slept or how work went. Forcing the prescribed load on a bad day degrades technique and raises injury risk. Working to RPE instead means the load adjusts itself to the day's condition: "three sets at RPE 8" is heavier when you are fresh and lighter when you are not, while the training stimulus stays comparable.
Beginners rate themselves poorly
Newer lifters consistently underestimate how much they have left — a set called RPE 8 may genuinely have five or more reps in reserve. Accuracy improves with experience. Until it does, occasionally taking a set to true failure and comparing your rating against the actual number of reps calibrates the scale quickly. For target loads, see the 1RM calculator.
RPE ⇔ RIR Reference Table
| RPE | 10 | 9.5 | 9 | 8.5 | 8 | 7.5 | 7 | 6.5 | 6 |
|---|---|---|---|---|---|---|---|---|---|
| RIR | 0 | 0.5 | 1 | 1.5 | 2 | 2.5 | 3 | 3.5 | 4 |
RIR (Reps in Reserve) = how many more reps you could have done. RPE = 10 − RIR (Helms et al. 2016). This tool uses "reps + RIR" as the effective rep max for 1RM estimation.
Glossary & FAQ
What is RPE?+
RPE 10: could not do another rep RPE 9: one rep left RPE 7: about three reps left
It is widely used in powerlifting and strength training.
What is the difference between RPE and RIR?+
RIR = 10 − RPE
RPE 8 means RIR 2 (two reps left), RPE 10 means RIR 0 (failure). This tool uses RIR to back-calculate your effective max reps and estimate your 1RM.
How is this different from a regular 1RM calculator?+
This tool factors in RPE (how much was left in the tank), working out how many reps you could have done to failure (reps + RIR) before estimating your 1RM — so it also works for sets stopped short of failure.
How do I get better at estimating RPE?+
When is RPE useful?+
・ Helms ER, Cronin J, Storey A, Zourdos MC. Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training. Strength Cond J. 2016;38(4):42-49. (RPE-RIR scale)
・ Zourdos MC, et al. Novel Resistance Training-Specific RPE Scale Measuring Repetitions in Reserve. J Strength Cond Res. 2016;30(1):267-275.
・ Halperin I, Malleron T, Har-Nir I, et al. Accuracy in Predicting Repetitions to Task Failure in Resistance Exercise: A Scoping Review and Exploratory Meta-analysis. Sports Med. 2022;52(2):377-390. (Systematic review and meta-analysis quantifying the accuracy of RIR estimation)
・ Epley B. Poundage chart. Boyd Epley Workout. 1985. (1RM estimation from effective reps)
RPE is a subjective measure and its accuracy depends on training experience and how well you read your own body. If your form breaks down or you feel joint pain, stop regardless of the RPE reading. This tool is for informational purposes only and does not replace professional coaching.
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