What Are RPE and Reps in Reserve?

Reps in reserve (RIR) is how many more repetitions you could have done at the end of a set. Rating of perceived exertion (RPE), as lifters use it, is the same idea on a 10-point scale: an RPE of 10 means you couldn’t have done another rep, 9 means one more, 8 means two more. Logging it beside reps and load tells you how hard a set really was, which kilograms alone can’t.

This article is general information, not medical advice.

The Scale

RPE	Reps in reserve	Meaning
10	0	Maximal: no more reps possible
9.5	0	No more reps, but slightly more load possible
9	1	One more rep possible
8.5	1 or 2	One more definitely, maybe two
8	2	Two more reps possible
7	3	Three more reps possible
5 to 6	4 to 6	Moderate effort

Zourdos and colleagues described this repetitions-in-reserve-based RPE scale for resistance training in 2016. In their study of 29 squatters, the RPE people gave tracked how fast they moved the bar: the slower the lift, the higher the rating, a sign that the ratings reflected real effort.

How Accurate Are People?

Judging reps in reserve is a skill. Zourdos’s group found that experienced lifters rated a true maximum more accurately than novices, and a 2022 meta-analysis by Halperin and colleagues found that people underestimate how many reps they have left by about one on average, with predictions more accurate closer to failure and in sets of 12 reps or fewer. Taking an occasional set to genuine failure, safely, recalibrates your sense of it.

How to Use It

• Set loads by feel on the day. A programme might call for “3 sets of 5 at RPE 8”: choose the load that leaves about two reps in the tank, which adjusts for a good or bad day.
• Keep most sets hard. Muscle growth increases as sets end closer to failure, while strength gains are similar across a wide range of effort, according to a 2024 meta-regression by Robinson and colleagues. Many programmes keep most working sets at RPE 7 to 9.
• Rate at the end of the set, right away, honestly, and judge by the rep you could still have done with good form.

Following It in Kaizora

Each strength training set on Fitness records its exercise, reps, load, RPE, and type (a warm-up, a drop set, or a set to failure), so a set’s effort stays with it in your history. Strength Training Sets Logged counts your sets, and Strength Training Volume Load adds up reps times load over working sets. Estimated one-rep maximums come from Brzycki’s equation and don’t use RPE, so sets at RPE 9 or 10 give the most meaningful estimates; see How to Estimate Your One-Rep Max Without Testing It.

The Short Version

• RPE 10 is no reps left; each point lower is about one more rep in reserve.
• Ratings close to failure are the most accurate; people underestimate reps left when far from it.
• Log RPE with every working set so effort, not just load, is in your history.

Sources

• Zourdos MC et al., “Novel resistance training–specific rating of perceived exertion scale measuring repetitions in reserve,” Journal of Strength and Conditioning Research 30, no. 1 (2016): 267–275. doi:10.1519/JSC.0000000000001049
• Helms ER et al., “Application of the repetitions in reserve-based rating of perceived exertion scale for resistance training,” Strength and Conditioning Journal 38, no. 4 (2016): 42–49. doi:10.1519/SSC.0000000000000218
• Halperin I et al., “Accuracy in predicting repetitions to task failure in resistance exercise: a scoping review and exploratory meta-analysis,” Sports Medicine 52, no. 2 (2022): 377–390. doi:10.1007/s40279-021-01559-x
• Robinson ZP et al., “Exploring the dose–response relationship between estimated resistance training proximity to failure, strength gain, and muscle hypertrophy: a series of meta-regressions,” Sports Medicine 54, no. 9 (2024): 2209–2231. doi:10.1007/s40279-024-02069-2