What Is RPE and RIR in Weightlifting?

RPE and RIR are two ways of describing the same thing: how close a set brought you to failure. RIR, reps in reserve, is the number of additional reps you think you could have done with good form. RPE, rate of perceived exertion, scores that same effort on a 1 to 10 scale, where RPE 10 means zero reps in reserve and RPE 7 means about three reps left in the tank. They are two labels for one idea, and once you can use either one, you have a much better tool for judging a set than just "that felt hard."

Weight on the bar alone does not tell you how hard a set actually was. The same 135 pounds for 8 reps can be an easy warm-up on one day and a near-max grind on another, depending on fatigue, sleep, and how many sets came before it. RPE and RIR give you a way to describe that difference.

What is RPE, exactly?

RPE, rate of perceived exertion, is a subjective 1 to 10 rating of how hard a set felt, adapted from the original Borg scale used in exercise science. In strength training, the scale is anchored to reps in reserve: RPE 10 is a set taken to true failure, RPE 9 means you could have done one more rep, RPE 8 means two more reps were possible, and so on. A study by Zourdos and colleagues validated this RIR-based RPE scale in experienced and novice squatters, finding it tracked closely with objective measures like bar speed, which supports it as a real, usable tool and not just guesswork.

Below about RPE 6, most people stop bothering to rate sets, since anything much easier than "four or more reps in reserve" is not really working weight for muscle or strength goals.

What is RIR, and how does it relate to RPE?

RIR, reps in reserve, is the same rating flipped around: instead of a 1 to 10 score, you just count how many more reps you believe you had left. The two describe the same effort:

Most people find RIR more intuitive to start with, since counting reps feels more concrete than assigning a score. Either one works, and plenty of programs mix the two depending on the exercise.

How many reps in reserve should you actually leave?

For most working sets aimed at building muscle or strength, 1 to 3 reps in reserve (RPE 7 to 9) is a well-supported target. Studies comparing sets taken all the way to failure against sets stopped a few reps short have generally found similar muscle growth between the two approaches, while training further from failure produces noticeably less fatigue and an easier recovery. That makes RPE 7 to 9 a good default: hard enough to be a real stimulus, without needing to grind every set into the ground.

This connects directly to a question we cover in detail in should you train to failure: the short answer is that failure has a place, but it is a tool for specific sets, not a default setting.

Why bother rating effort instead of just picking a weight?

Because a fixed weight does not account for how you actually feel that day. On a well-rested day, your usual 5-rep weight might be an RPE 7. On a rough night's sleep, the same weight and reps can be an RPE 9. Rating by RPE or RIR instead of a fixed number lets your training adjust to your real capacity in the moment, rather than forcing the same load regardless of how recovered you are.

This is also a natural way to progress over time within a rep range: as a weight starts feeling easier at the same RIR, that is a sign it is time to add load, which is exactly how progressive overload shows up set to set rather than just week to week.

How do you get better at judging RPE and RIR?

By checking your estimate against what actually happened. If you stop a set at "2 reps in reserve" and then, out of curiosity, push it to see how many more you actually get, you will often find your estimate was off, especially early on. Doing this occasionally, and comparing your rated effort to your logged reps over weeks, is how the skill sharpens. It gets noticeably more accurate after a few months of consistent training.

Manually cross-checking every set against a spreadsheet is exactly the kind of tracking that falls off after a couple of weeks. OneFit logs the weight and reps behind every set automatically, so when Ori suggests a target based on how a movement has been trending, you have the actual history to check your RPE calls against instead of relying on memory.

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FAQ

What is RPE in weightlifting? RPE stands for rate of perceived exertion, a 1 to 10 scale for how hard a set felt. RPE 10 means you could not have done another rep, RPE 9 means you had one rep left in you, and so on down the scale.

What does RIR mean? RIR stands for reps in reserve, the number of additional reps you believe you could have done with good form before failing. It is the same idea as RPE, just counted the other direction. 2 RIR and RPE 8 describe the same set.

How many reps in reserve should you leave on most sets? For most hypertrophy and strength training, 1 to 3 reps in reserve on most working sets is a well-supported range. That is hard enough to drive progress without grinding every set to failure and piling up unnecessary fatigue.

Is RPE accurate for beginners? It takes practice. New lifters often misjudge how close they are to failure in both directions, so RPE and RIR estimates get more accurate with a few months of training experience. Logging your actual rep counts alongside your RPE rating speeds up that learning curve.

Do you need to train to RPE 10 to build muscle? No. Research comparing sets taken to failure against sets stopped a few reps short generally finds similar muscle growth, with less fatigue and better recovery when you leave a rep or two in reserve. RPE 10 has a place, but not on every set.