What is Reps in reserve (RIR)?

Reps in reserve, or RIR, counts how many more clean reps you had left when you stopped a set. If you finish a set and feel you could have done two more, that set was at 2 RIR. It is the mirror image of RPE, where a 10 means zero reps in reserve.

Most people find RIR easier to understand than a 1 to 10 number. As a beginner, many coaches suggest stopping most sets with about 1 to 3 reps left, which builds skill without wearing you out. For example, if you curl 12 kg and manage 10 reps but could have done 12, you were at 2 RIR.