What are RPE and RIR?

RPE: the perceived exertion scale

RPE (rating of perceived exertion) is a scale on which you score your effort subjectively. Its origins lie in Borg's classic scale; the version in common use today runs from 0 to 10: 0 is rest, 3–4 comfortable work, 6–7 clear effort, 8–9 serious effort, and 10 the limit of what you can do that day. Being subjective is a feature rather than a flaw: on a day after a bad night's sleep the same weight produces a higher RPE, and the scale reflects that reality automatically. Fixed programmes cannot see this; RPE can.

RIR: reps in reserve

RIR (reps in reserve) is a more concrete measure specific to strength training: when the set ended, how many more reps could you have done with good technique? If the answer is 3, you worked at 3 RIR; if it is 0, you worked at your technical limit. The strength of RIR is that it is countable; it gives clearer information than a feeling of “that was hard”. The two scales link like this: RPE ≈ 10 − RIR, so RPE 8 is roughly 2 RIR and RPE 9 roughly 1 RIR. Which you use is a matter of preference; RIR is usually more practical on strength sets and RPE on cardio.

What these scales are for

There are three main uses. Choosing loads: a target of “8–12 reps at 2–3 RIR” lets you find the appropriate weight without testing; this method is applied in the starting weight guide. Daily adjustment: holding the same RIR target on a tired day automatically lowers the weight and prevents overreaching. Tracking progress: if the same weight produces a lower RPE over time, you are getting stronger, and that is the signal for progressive overload.

Calibration for beginners

Estimating RIR is a skill, and everyone gets it wrong at first; research shows that beginners generally underestimate their reserve, saying “one rep left” when in fact three or four remain. This is normal and improves with practice. A safe drill for calibration is to take a set with a light weight close to the point where technique breaks down, and to see the gap between your estimate and reality. The general framework for beginners is this: most working sets should stay in the 2–3 RIR range; going to 0 RIR, that is to complete exhaustion, is not necessary for technique or recovery.

How to write it down and how to read it

RPE and RIR come into their own when combined with records. The common notation is simple: a line reading “Chest press 40 kg × 10 @RPE 7” says that 10 reps were done with 40 kg and that the set finished at a difficulty of 7, roughly three reps in reserve. The value of that third column emerges over time: a notebook recording only weight and reps suggests progress has stopped when it shows the same numbers, whereas the RPE column makes visible that those same numbers are getting easier, that is, that development is continuing. If the RPE for the same weight and reps has fallen from 8 to 6, the ground is ready for an increase. It also warns in the other direction: if the RPE of every exercise rises systematically over weeks, fatigue may be accumulating, and what needs reviewing is rest rather than the programme. This simple three-column record is a zero-cost tool that lets you tell progress, stagnation and overreaching apart at a glance.

Limits and common mistakes

RPE and RIR do not measure pain, and the distinction between effort and pain is critical. A burning sensation in the muscle is part of effort; sharp, stabbing or one-sided pain in a joint is a reason to stop the set whatever the RPE, and to speak to a healthcare professional if it recurs. The second common mistake is taking every set to RPE 9–10; sustainable development mostly happens in the moderate difficulty zone. The third is using the scale to compare yourself with others: RPE is personal by definition, and your 7 is only your 7.

Frequently asked questions

This guide draws on the tradition of Borg's perceived exertion scale and on the general findings of resistance training research into RIR-based load adjustment.