RPE and RIR are two closely linked ways of describing training effort, and lifters often use the terms almost interchangeably. Here's exactly how they relate, where they diverge, and which one tends to be easier to learn.
RPE (Rate of Perceived Exertion) is a 1–10 scale rating how hard a set felt overall. RIR (Reps in Reserve) is a more concrete underlying question: how many more reps, with good form, could you have performed? In the resistance-training-specific framework described by Zourdos et al. (Journal of Strength and Conditioning Research, 2016), RPE is essentially built on top of RIR — each RPE score has a defined RIR-based description, such as "RPE 9 = 1 rep in reserve."
Reps in reserve (RIR) estimates how many additional repetitions you believe you could have completed with good technique before reaching muscular failure. It's the concrete, countable half of the RPE/RIR framework described by Zourdos et al. (Journal of Strength and Conditioning Research, 2016):
RIR becomes less precise to estimate the further a set is from failure — research on RIR-based RPE has found lifters commonly underestimate their true reps in reserve, especially at 3–4 RIR. Convert RIR to RPE (or back) instantly with our RPE Calculator.
| RPE | RIR |
|---|---|
| 10 | 0 |
| 9 | 1 |
| 8 | 2 |
| 7 | 3 |
| 6 | 4 |
Half-point RPE values (9.5, 8.5, 7.5, 6.5) sit between the two nearest whole-number descriptions — for example, RPE 8.5 is described as "1 to 2 reps in reserve" rather than a precise fractional rep count. You can convert instantly between the two using our RPE Calculator, or see the full breakdown in our RPE Chart.
RPE and RIR are directly linked by definition in this framework, so they don't disagree about a specific set — but they differ in what a lifter is actually asked to judge. RPE asks for a single overall effort rating; RIR asks a more specific, countable question. Some coaches find that asking "how many reps did you have left?" produces a more consistent answer than asking "how hard did that feel out of 10?", because RIR anchors the rating to something concrete rather than a purely subjective effort sensation. In practice, most programs use whichever term the coach or app prefers — the underlying framework is the same.
Accuracy also differs by distance from failure for both: research on RIR-based RPE has consistently found that lifters underestimate their true reps in reserve, and this effect grows larger the further a set is from failure. A rating of "3 RIR" (RPE 7) is less precise, on average, than a rating of "1 RIR" (RPE 9), for both terms.
| Set | Described as RPE | Described as RIR |
|---|---|---|
| 100 kg squat × 5, felt very hard | RPE 9 | 1 RIR |
| 60 kg bench × 8, comfortable | RPE 7 | 3 RIR |
| 140 kg deadlift × 1, true max | RPE 10 | 0 RIR |
Many coaches find RIR more intuitive for people new to autoregulation, because "how many more reps could I have done?" is a concrete, countable question, whereas "rate this set out of 10" can feel more abstract without a reference point. That said, both require practice — a beginner's RIR estimate is typically just as unreliable as their RPE estimate until they've built genuine calibration through experience, ideally with feedback from a coach or training partner. See our full guide on calibrating RPE as a beginner for more detail.
RPE and RIR are two vocabularies describing the same underlying idea: autoregulation, or adjusting training load based on how a lifter is actually performing that day rather than a fixed percentage set weeks in advance. Whichever term a program uses, the goal is the same — use a subjective-but-structured rating of effort to keep training intensity appropriate for daily readiness, rather than rigidly following a number that may no longer match how the lifter is actually feeling.
Use the RPE Calculator to convert RPE to RIR (or back), estimate a working weight from your 1RM, or get an RPE-adjusted estimated 1RM.
Open the RPE Calculator →What does RIR mean?
RIR stands for Reps in Reserve — an estimate of how many more repetitions you could have completed with good technique before reaching muscular failure. See "What Does Reps in Reserve (RIR) Mean?" above for what each value from 0 to 4 means in practice.
What is the difference between RPE and RIR?
RPE is the overall 1-10 rating of how hard a set felt. RIR (reps in reserve) is the more concrete count underneath it: how many more reps you believe you could have completed. In the resistance-training framework used today, the two are directly linked, but RIR becomes harder to estimate accurately as you move further from failure.
How do you convert RPE to RIR?
Using the Zourdos et al. (2016) framework: RPE 10 = 0 RIR, RPE 9 = 1 RIR, RPE 8 = 2 RIR, RPE 7 = 3 RIR, RPE 6 = 4 RIR, with half-point RPE values falling between the two nearest whole numbers.
Is RIR easier for beginners than RPE?
Many coaches find RIR more intuitive for beginners because it asks a concrete question (how many more reps could you do?) rather than an abstract effort rating. Both still require practice to rate accurately, and both scales feed into the same underlying resistance-training framework.