Workout Wizard

What are RIR and RPE in lifting, and how do you use them?

By Workout WizardDegree in Sport Science, MSc in Sports Physiology, PhD candidate in Sports PhysiologyUpdated November 4, 2026, a 9-minute read

On this page
  1. The RPE scale for lifting, in reps in reserve
  2. How well can you judge your reps in reserve?
  3. How close to failure should you train for muscle growth?
  4. RIR or percentages of your max?
  5. How to get better at judging RIR
  6. RIR or RPE: which should you use?
  7. How Workout Wizard does it
  8. Using RIR and RPE in your training
  9. References

RIR (reps in reserve) is how many more reps you could have done when you end a set. RPE (rating of perceived exertion) puts the same idea on a 1–10 scale: RPE 10 is failure, 9 leaves one rep, 8 leaves two and 7 leaves three. For muscle growth, end most sets about 0–3 reps short of failure. Lifters guess about one rep too few on average, so most sets sit a little further from failure than they feel. The two scales convert one to one (RPE = 10 − RIR), so use the one your program is written in.

The RPE scale for lifting, in reps in reserve

The lifting RPE scale was tested by Zourdos and colleagues in 2016, after powerlifting coaches had used a version of it for years. Each number stands for a count of reps left (Zourdos et al. 2016):

RPE What it means RIR
10 Maximum effort 0
9.5 No more reps, but you could have added a little weight 0
9 1 rep left 1
8.5 1–2 reps left 1–2
8 2 reps left 2
7.5 2–3 reps left 2–3
7 3 reps left 3
5–6 4–6 reps left 4–6
1–4 Light to little effort Far from failure

In the same study, lifters with about five years of squatting rated a true one-rep max 9.8 on average. Lifters with less than a year rated it 9.0, as if they still had a rep left.

If you searched for the RPE scale for running or cycling, that is Gunnar Borg’s scale. It rates whole-body effort from 6 to 20, or from 0 to 10 in his later category-ratio version (Borg 1982). It fits lifting poorly: bodybuilders who took sets of squats and bench press to failure still rated them below the top of a classic RPE scale (Hackett et al. 2012). Tying each number to the reps left solves that, and the rest of this guide is about the lifting scale.

How well can you judge your reps in reserve?

Within about a rep, on average, and better near failure. A meta-analysis pooled 12 studies, 414 people in all, in which lifters predicted their reps left and then kept going to failure. They predicted about one rep too few (0.95 reps, with wide differences between studies). Predictions were a little more accurate close to failure, in later sets, and in sets of 12 reps or fewer. Sets longer than 12 reps were much harder to judge, and training experience made no clear difference (Halperin et al. 2022).

Predicting too few reps means you think you’re closer to failure than you are. A set you call 2 RIR is, on average, nearer to 3.

Two later studies in trained lifters fit that picture:

  • On the bench press at 75 % of 1RM, 24 trained men and women called out 1 and 3 RIR within about two-thirds of a rep of the truth, on average, with a slight lean toward predicting too few. Sex, years of training and strength made no difference (Refalo et al. 2024b).
  • Nine trained men took a bench press set to failure three times a week for six weeks. The size of their errors didn’t shrink, and they underestimated their reps left more in later sessions and in longer sets (Remmert et al. 2023).

How close to failure should you train for muscle growth?

Closer tends to grow more muscle, though going all the way to failure adds little. An analysis that pooled dozens of studies found that growth rose as sets ended closer to failure, while strength gains barely changed across a wide range of RIR. The authors had to estimate each study’s RIR from its description and called the result exploratory (Robinson et al. 2024).

Taking sets all the way to failure hasn’t beaten stopping a rep or two short. An earlier meta-analysis of 15 studies found no growth advantage for sets taken to momentary failure over sets stopped short (Refalo et al. 2023). And when one leg trained to failure on the leg press and leg extension and the other stopped 1–2 reps short, the quadriceps grew by the same amount in 8 weeks: 0.181 cm against 0.182 cm. The failure leg lost more reps and bar speed within each session (Refalo et al. 2024a).

Ending most sets 0–3 reps short of failure fits all three, as the guide to progressive overload, week by week says. Our reading, which no study has tested: since a set you call 3 RIR may be closer to 4, aim for 1–2 RIR on the sets you want to count, and keep true failure for exercises where failing is safe. Sets near failure also need longer rests to keep your reps up (see how long to rest between sets).

RIR or percentages of your max?

Choosing the weight by effort has done at least as well as fixed percentages of a tested max:

  • In 21 trained men on 8 weeks of squats and bench press with matched sets and reps, one group lifted set percentages of their 1RM and the other picked loads to hit target RPE ranges. Both gained strength and muscle thickness with no significant difference, and the RPE group’s strength gains ran slightly higher (squat +17 kg against +14 kg, about 38 lb against 31) (Helms et al. 2018).
  • In 31 trained men squatting twice a week for 12 weeks, the RIR group ended up lifting heavier, about 83 % of 1RM on average against 80 %, and gained more: +11.7 % against +8.3 % on the front squat and +10.8 % against +7.1 % on the back squat (Graham & Cleather 2021).
  • A meta-analysis of six trials that set the load by effort or bar speed found no clear 1RM difference (about 2 kg, p = 0.09) (Hickmott et al. 2022).

Most of these trials measured strength. The one that measured muscle found similar growth with both methods. The case for RIR is that it moves with you: a percentage of last month’s max gets easier as you get stronger, and it can’t tell that you slept badly, while an RIR target keeps each set about equally hard. A percentage still makes a good first guess for the weight, and the one-rep max calculator turns any recent set into an estimated max and a table of percentages.

How to get better at judging RIR

The usual advice comes from the paper that set out how to apply the scale. Rate your sets and log the number with your weights and reps, and test yourself before you rely on it: rate a set, then repeat the same weight to failure and count how many reps you had left (Helms et al. 2016). Whether that practice makes you more accurate hasn’t been shown. In the six-week study above, regular sets to failure didn’t make the errors smaller (Remmert et al. 2023).

Some habits that follow from the accuracy data and from safety:

  • Make the call near the end of the set, when predictions are most accurate
  • Learn on sets of 12 reps or fewer, which are easier to judge
  • Test failure where failing is safe: machines, cables, curls and raises, or a squat or bench press with safety pins or a spotter
  • Expect your error to lean one way: if the test set beats your guess, you’ve been stopping early

RIR or RPE: which should you use?

They measure the same thing, so pick by what the number has to do. RIR reads naturally on typical muscle-building sets, where “two left” is easier to picture than “an 8”. RPE’s half points and its 9.5 (“no more reps, but more weight was possible”) help on heavy singles and doubles, which is why the scale took hold in powerlifting. If your program says RPE 8, stop with two reps left. If it says 2 RIR, that’s RPE 8. Keep Borg’s scale for your cardio.

How Workout Wizard does it

Workout Wizard counts effort in reps in reserve. Each week of a training block has a target RIR, shown on the workout card, and the weeks ask for a little more effort as the block goes on, before a lighter deload week.

From the second week, each set comes with a suggested weight and reps that aim at that week’s RIR. As you type your reps, the app shows the target, for example “12 reps or 1 RIR”. In the first week, or on a set without a target, you choose the weight and stop at the week’s RIR. You don’t rate each set: you log the weight and reps you did, and the next week’s suggestions start from them.

None of the studies above tested this exact scheme. It is one structured way to keep sets within a few reps of failure and ask for a little more as the weeks go by.

Using RIR and RPE in your training

Stop most sets 0–3 reps short of failure, about 1–2 on the ones you want to count, and read RPE as 10 minus your reps left. Expect to guess about a rep too few, make the call near the end of sets of 12 reps or fewer, and check yourself now and then with a set to failure on a safe exercise.

References