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RPE and RIR: how to rate how hard a set was

Q: What does RPE 8 mean?

You could have done two more reps after the set, so 2 RIR.

Q: Which RPE should I pick?

Research doesn't prescribe an exact number. Setonomy recommends RPE 7–9, or 1–3 reps in reserve, as a guideline, and RPE 8 to start.

By Setonomy · published October 24, 2026, updated October 27, 2026

RPE stands for “rating of perceived exertion.” On the RPE scale for strength training, levels 5 to 10 count how many more reps you could have done at the end of a set: RPE 8 means two reps in reserve, or 2 RIR, and RPE 10 means none^[1].

The RPE chart

The table shows the scale as Zourdos and colleagues described it in 2016. Below RPE 5, it only describes how easy a set felt^[1]^[2].

RPE and reps in reserve (RIR)
RPE	RIR	How the set felt
10	0	Maximal effort, not one more rep
9.5	0	No more reps, but the same reps would have worked with a little more weight
9	1	One more rep was possible
8.5	1–2	One more for sure, maybe two
8	2	Two more reps were possible
7.5	2–3	Two more for sure, maybe three
7	3	Three more reps were possible
5–6	4–6	Four to six more reps were possible
3–4	–	Light effort
1–2	–	Little to no effort

Half steps like 8.5 stand for a range: one more rep for sure, maybe two. RPE 9.5 sits between 9 and 10: another rep wouldn't have worked, but the reps you did would have, even with a little more weight^[1]. From four reps in reserve, the scale groups several together, because a reserve that large is hard to pin down^[2].

RPE and RIR: two numbers for the same thing

RIR stands for “reps in reserve.” On the strength training scale, the two numbers are tied together: RPE 10 is 0 RIR, RPE 9 is 1 RIR, and so on^[1]. That's why you can plan with either, for example “3 × 10 at RPE 8–9” or “3 × 10 with 1–2 RIR”^[2].

The first RPE scale came from Gunnar Borg. It ran from 6 to 20 and was mainly meant for endurance exercise. According to Helms and colleagues, a scale based on reps in reserve already appeared in a powerlifting training manual in 2008; Zourdos and colleagues introduced it into research^[1]^[2].

Why train by RPE?

If you plan only by percentage of your max, you need an up-to-date 1RM, the weight you can lift for exactly one rep. But strength varies from day to day, for example with sleep, nutrition and stress, and a test can catch an especially good or bad day^[2]. The 1RM test is considered reliable; between two tests, the median coefficient of variation was 4.2%, so results differ by a few percent^[3].

On top of that, how many reps you can do at a given percentage differs from person to person. An analysis of 269 studies with 7,289 participants accounts for that spread; it needs separate tables for the leg press and the bench press, because more reps were possible on the leg press^[4].

RPE, on the other hand, adjusts the load to the day: if a set goes easier than planned, the next one can be heavier; if it feels harder, it gets lighter^[2].

How accurate is the rating?

It works best close to failure. In the study that introduced the scale, experienced squatters rated their max attempt in the test at RPE 9.80 on average, while beginners with an average of 0.4 years of training rated it at 8.96. The authors give two possible reasons: a single rep is harder to rate, or the beginners hadn't yet reached their true max in the test^[1].

Further from failure, it gets less accurate. Participants rated a single rep at 75% of their max at about RPE 5 on average, with individual ratings ranging from 3 to 7. The authors suggest that the lighter the set, the bigger the error in estimating the reserve^[1].

A meta-analysis of 12 studies with 414 participants paints a similar picture. On average, participants underestimated their remaining reps by just under one (0.95), but the studies varied widely. Predictions got slightly better close to failure and in sets of 12 reps or fewer, and barely in later sets; training experience made no apparent difference^[5].

So whether experience helps is still open. If you're new to the scale, you can start by just logging your ratings and checking them now and then: rate a set that stops short of failure, then do a set with the same weight to failure^[2].

Which RPE is right?

Research doesn't give one fixed number. The American College of Sports Medicine's 2026 position stand names sets close to failure or a target of 2–3 reps in reserve as ways to reach enough effort, but notes that the evidence is insufficient to set exact RIR or perceived exertion targets^[6].

You don't have to go to failure for that: according to the position stand, taking sets to momentary muscular failure doesn't add gains in strength or muscle growth and isn't needed for results^[6].

RPE in Setonomy

In Setonomy, turn on RPE under Settings → Effort (RPE) → “Use target RPE.” That's also where you choose your target RPE.

The Effort (RPE) settings in Setonomy: “Use target RPE” is on, “Hard,” or RPE 9, is selected as the target RPE, followed by the recommendation of RPE 7–9 and, under “Input during workout,” the choice between “Simplified” and “Slider” — Settings → Effort (RPE): the switch at the top, then your target RPE with the recommendation and the workout input, which applies to this device only.

The workout then asks after every set: “How hard did the set feel?” You choose Easy, Medium, Hard or Max, which is RPE 7, 8, 9 and 10. After you tap, a line below shows what the value means, for example “RPE 8 · 2 more reps would have been possible”; on small iPhones, that line is left out.

The set card in Setonomy: Bench Press, set 1 of 3, target 8 reps at 180 lb, with the suggestion 8 × 185 lb and last time's 8 × 180 lb, then the RPE choice set to “Medium” and “RPE 8 · 2 more reps would have been possible” — The set card: “Medium” is selected, and below it you see what RPE 8 means. A line at the top explains the suggestion.

Instead of the four buttons, “Input during workout” also offers a slider from 1 to 10 in half steps.

The set card with the slider: Bench Press, set 1 of 3, target 8 reps at 180 lb, “Last time your sets averaged RPE 7.7; your target is 9” at the top, and the RPE slider with the question “How hard did the set feel?” at the bottom — The slider starts out grayed at your target RPE, 9 here. The value is only recorded once you drag it; then the line above the slider shows what it means.

With the four buttons, the set's Notes (ⓘ) show a table of the levels with the reps that were left.

The set's Notes in Setonomy: the suggestion with “Average RPE 7.7, below your target of 9,” the warm-up, the “Simplified RPE” table with Easy, Medium, Hard and Max for RPE 7 to 10 and 3, 2, 1 and no reps left, and “Last time” with 8 × 180 lb — The set's Notes (ⓘ): the reason for the suggestion at the top, the “Simplified RPE” table in the middle.

The target RPE applies to all exercises. Setonomy recommends RPE 7–9, or 1–3 reps in reserve, as a guideline, and RPE 8 to start. From the target, Setonomy works out next time's suggestions: if your sets averaged more than half a point harder than the target, the app recalculates the weight for the target: less, by up to about 10% or, for light weights, one step, or the same if the math lands on the same step; the reps stay the same. For exercises without weight and at the lightest load, you get fewer reps instead. If your sets were easier, it can go up. The reason appears in a line above the set or, if another note is shown there, in the Notes (ⓘ).

Setonomy also estimates your 1RM from hard sets; RPE 9.5 counts as half a rep in reserve there. Personal records count sets with fewer than 10 reps at RPE 8.5 or higher, which with the buttons means “Hard” and “Max.” If an exercise has no such set yet, the app asks you for a calibration set.

During a workout, the “… completed” card after each exercise except the last shows the Avg RPE; in your history, it appears for each exercise, along with the RPE of every set. All of this is free; with Premium, comparing two workouts also puts their Avg RPE side by side. More in help on training.

Frequently asked questions

What does RPE 8 mean?

You could have done two more reps after the set, so 2 RIR^[1].

What's the difference between RPE and RIR?

RIR counts the reps you had left; RPE rates the effort from 1 to 10. For whole numbers from RPE 7 to 10, the two add up to ten, so RPE 9 is 1 RIR^[1].

What does RPE 9.5 mean?

Another rep wouldn't have worked, but the reps you did would have, even with a little more weight^[1].

For example: 5 reps at 225 lb, and a sixth won't go. But 5 reps at 230 lb would still have worked, so the set was just short of your limit. At RPE 10, even 230 lb wouldn't have gone for 5.

Do I need experience to use RPE?

In the 2016 study, experienced lifters rated their max attempt closer to RPE 10 than beginners did^[1]; in a meta-analysis, training experience made no apparent difference^[5]. It helps to check your ratings now and then with a set taken to failure^[2].

Which RPE should I pick?

Research doesn't prescribe an exact number^[6]. Setonomy recommends RPE 7–9, or 1–3 reps in reserve, as a guideline, and RPE 8 to start.