RPE–RIR Converter
The RPE–RIR Converter translates between the two common scales that describe training intensity: perceived exertion (RPE) and the number of repetitions left in reserve (RIR).
Most modern training programmes no longer write down weights alone; they use expressions such as “5 reps at RPE 8” or “leave 2 RIR”. Both languages describe the same thing — how hard a set is to be taken — but they look at it from different directions. This tool converts quickly between the two scales, so that you can render the wording in your programme into the language you are used to.
Tool
Frequently asked questions
Which is better, RPE or RIR?
The two give the same information in different languages; use whichever you find easier to think in. RIR stands out for its concreteness in low-repetition strength work, while RPE stands out for its flexibility on long sets and in cardio-type work.
What are values below RPE 7 good for?
Warm-up sets, technique work and recovery days sit in the low RPE zone. Not every set needs to be demanding; a significant part of a good programme is deliberately spent in the comfortable zone.
I cannot estimate my reserve accurately — what can I do?
This is very common and improves with time. Occasionally taking a set to the genuine repetition limit on a safe accessory movement and comparing the outcome with your estimate is the most practical way to calibrate your own scale.
Are these scales used in activities such as running?
RPE, yes; perceived exertion is a common management tool in endurance sports. RIR, because it rests on the notion of repetitions, is only meaningful in resistance training.
Method and formula
The conversion rests on the correspondence between the 0–10 RPE scale established in resistance training and RIR, the number of reps in reserve: RPE 10 means there are no repetitions left in reserve (RIR 0); RPE 9 corresponds to roughly 1 repetition in reserve (RIR 1), RPE 8 to roughly 2 repetitions in reserve, and the table continues downwards in the same way. The tool reads the equivalent of the value you enter from this conversion table; intermediate values, RPE 8.5 for example, are interpreted as half a repetition in reserve.
How to read the result
Both scales rest on subjective judgement, and they grow more accurate with experience: beginners usually underestimate their reserve, so a set where they say “one rep left” often has three or four more in it. The conversion itself is mechanical; the real skill is learning to score your own exertion accurately. Occasionally taking a set genuinely to the repetition limit, on a suitable and safe movement, sharpens that calibration.
Limits
- Both scales are subjective; one person’s RPE 8 may not correspond to the same real difficulty as another’s.
- Estimating RIR becomes harder on high-repetition sets, where the burning sensation masks the true reserve.
- The conversion table is an approximation; the relationship between RPE and RIR varies slightly from one source to another.
- The scales take no account of technical breakdown; once form starts to fail, the set should be ended whatever the reserve.
Safety boundary
Working often in the RPE 9–10 zone strains recovery and raises the risk of technical errors; building the bulk of a programme from sets with repetitions in reserve is a common and cautious approach. Do not confuse pain with the sensation of difficulty; a set that causes pain should be stopped whatever its RPE value.
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