RPE vs RIR: What's the Difference and Which Should You Use?

If you've followed a strength program, you've probably seen sets written as "RPE 8" or "2 RIR." In lifting, RPE vs RIR comes down to two ways of describing the same effort. Outside the weight room, only one of them works, and knowing the difference helps you track training more accurately.

RPE: rating of perceived exertion

RPE stands for rating of perceived exertion: how hard something feels, usually on a 1 to 10 scale. It started in endurance and sport science and works for any kind of training. Coaches often use session RPE, a single rating for a whole workout multiplied by its length in minutes, to estimate training load.

In strength training, RPE took on a more specific meaning. A 2016 study by Zourdos and colleagues introduced a lifting scale that ties RPE numbers to reps left in the tank: RPE 10 means no reps left, RPE 9 means one, RPE 8 means two, and so on. Powerlifting coach Mike Tuchscherer is widely credited with popularizing it.

Good at: working across every kind of training, from a heavy squat set to a sparring session. Weak spot: a broad 1 to 10 rating can mean different things to different people unless they anchor it carefully.

RIR: reps in reserve

RIR stands for reps in reserve: how many more reps you could have done with good form before failing. A set at "2 RIR" means you stopped with about two reps left.

Good at: being concrete. "How many more could I have done?" is an easier question to answer honestly than "how hard was that?" Weak spot: it only works for sets with a clear failure point, like lifting. It doesn't translate to a run, a practice, or a roll.

How accurate is it? A 2021 meta-analysis by Halperin and colleagues found lifters tend to underestimate their reps in reserve by about one rep on average. Estimates also tend to be more accurate closer to failure and on sets of 12 reps or fewer.

The verdict: use each where it fits

For individual lifting sets, RPE and RIR are two labels for the same idea, so use whichever your program uses. RPE 8 and 2 RIR are close to interchangeable. Expect to be off by a rep now and then, especially early in a set.

For everything else, including whole sessions, conditioning, and skill practice, use a simple 1 to 10 session RPE. It's the only one of the two that lets you compare a lifting day to a hard practice, which matters if you want to track your overall training load through meet prep or a fight camp, when lifting, conditioning, and skill work stack up.

Log effort for every session

You can rate sessions in any notebook. Sherpa is a free athlete journal that records an effort rating and duration after each session and shows how your training load changes over time across lifting, practice, cardio, and mobility. Download Sherpa on the App Store.