RPE rates effort on a 1–10 scale; RIR estimates how many repetitions were left before failure. This page provides a definition and practical context; it is not an individualized medical or nutrition prescription. Use the related tools and guides for calculations or programming decisions rather than treating a glossary definition as a result.
Use the RPE and RIR calculator to convert a recent set into an estimated load range, including a worked example that walks through the RPE-to-RIR conversion step by step.
Choosing which one to use
RPE and RIR describe the same underlying concept from opposite directions: RPE rates how hard a set felt on a 1 to 10 scale, while RIR counts the reps left more literally. In practice, RIR is often easier for beginners to internalize (counting reps is a more concrete task than rating a feeling), while RPE is the more common convention in published research and established programs like RPE-based powerlifting templates. See the full RPE entry for the conversion table between the two and the calibration check that helps new lifters correct for under-rating their own effort.
Practical autoregulation guidelines
In training routines targeting hypertrophy, aim for sets in the 1 to 3 RIR range (RPE 7 to 9). This guarantees that motor units are fully recruited without accumulating unnecessary neuromuscular fatigue from training to absolute muscular failure on every exercise.