RIR explained: what reps in reserve means and how to log it

RIR, or reps in reserve, is how many more clean reps you think you could have done when you ended a set. If you racked the bar at 8 reps and had 2 more in you, that set was 2 RIR. Log it as one number after each working set, and expect your guesses to run about one rep low: a 2022 review of 12 studies found lifters underestimated how many reps they had left by just under 1 rep on average.

RIR turns "that felt hard" into a number you can compare week to week. It's often one of the first places a cutting diet shows up in the gym, because the same weight can start to feel harder before your rep count drops.

Disclosure: I make Arrow, an iPhone app that logs workouts and food together, including RIR on each set. Competitor details come from each company's own help center or App Store listing, checked 2026-11-10. The bench log below is illustrative, not a real user. Spot something out of date? Email support@arrowfitnessapp.com.

01How does RIR compare with RPE?

They measure the same thing from opposite ends. RPE (rating of perceived exertion) in lifting is a 10-point scale where each point below 10 is one rep in reserve. Zourdos and colleagues published that version in 2016, and Strong's help center uses the same mapping:

Strong's help center says ratings below RPE 6 are too subjective to measure well, so it leaves them out. MacroFactor Workouts logs RIR from 0 to 6+, where 6+ just means the set was very easy.

02How accurate is your guess?

Accurate enough to train with. The guesses get closer near the end of a hard set. In Zourdos' study of 29 squatters, RIR-based ratings tracked bar speed closely in both experienced lifters and novices (a correlation of -0.88 in the experienced group and -0.77 in novices), so slower reps got rated as harder.

Halperin and colleagues' review pooled 12 studies with 414 people and found three useful patterns:

• On average, people underestimated their remaining reps by 0.95.
• Guesses got more accurate closer to failure and on sets of 12 reps or fewer.
• Training experience didn't make much difference.

So if you log 3 RIR on a set of 15, you probably had more than 3 left. On a heavy set of 5 that you rate at 1 RIR, you're likely close. MacroFactor's help center notes that it may take a few sessions on a new exercise to dial in your estimates, and that the number doesn't need to be perfectly precise to be useful.

03How do you log RIR without slowing down?

• Log working sets only, and skip warm-ups.
• Use whole numbers (0, 1, 2, 3) and write 4 for anything easier.
• Log it the moment you rack the bar, before the rest timer starts. If you wait until the end of the workout, every set turns into a 2.
• Be most careful on the last set of each exercise, since that's usually the one a progression rule reads.

To check your guesses, once in a while take the last set of a safe exercise, such as a machine press or a leg extension, to the point where you can't complete another rep, and compare what you got with what you predicted. Don't do this on heavy squats or bench without a spotter.

04What does RIR show that reps don't?

Here's an illustrative 4-week bench log: 3 sets of 8 at a target of 1 to 2 RIR. The rule is that if all three sets hit 8 reps and the last set still had at least 1 rep left, you add 5 lb next week. If any set misses 8, you keep the weight.

Look at set 2 in weeks 2 and 3. It's 8 reps at 160 lb both times, but it went from 1 RIR to 2 RIR. A log with only reps and weight would show no change. The RIR column is how you see that you got stronger.

The same column works the other way. If you're cutting and a set that used to leave 2 reps in reserve now leaves 0 at the same weight for two or three sessions, that's often the first sign the deficit is costing you strength, before the rep count drops. The rest of those signs are in is my deficit too aggressive?. On a bulk, the opposite pattern, the same weight feeling easier week after week, is a good sign your food is supporting your training.

05Do you need to train to 0 RIR?

Probably not for muscle growth. Refalo and colleagues' 2023 meta-analysis of 15 studies found no advantage for training to momentary muscular failure over stopping short of it. With looser definitions of failure, they found only a trivial advantage. Stopping 1 to 3 reps short on most working sets is a reasonable default, and it makes your RIR numbers more useful, since a set at 0 can't tell you how much you had left.

06Which apps log RIR or RPE?

From each app's own help center or App Store listing, checked 2026-11-10:

• MacroFactor Workouts logs RIR on every set (0 to 6+) and uses it to shape its weight and rep recommendations. If you want an app to choose your next weights from RIR, it does that better than Arrow today.
• Strong logs RPE on a 6 to 10 scale and publishes the RIR mapping above.
• Hevy logs RPE alongside weight, reps and duration.
• Arrow logs RIR on each set and uses a rep-range rule for progression: when you top out the range, the next session's target moves up. We haven't published whether RIR itself changes that target. Your food log and weight trend are in the same app, so if your bench leaves 0 RIR at a weight that used to leave 2, the calorie and protein numbers that might explain it are already in the same log. Arrow is one paid subscription with no free version (7-day free trial, price shown in the App Store), and the current version is iPhone only.

If you'd rather use RPE, Strong and Hevy both support it, and the table above converts between them. For the full method of adding weight and reps over time, see how to track progressive overload. To compare the apps on everything else, see best workout tracker apps for iPhone.

07FAQ

Is RIR the same as RPE?

They measure the same thing. RPE 8 means 2 reps in reserve, and RPE 10 means 0.

What RIR should I train at?

Most working sets at 1 to 3 RIR is a sensible start. Your program may set its own targets.

Should beginners log RIR?

Yes, even if the first few weeks are rough guesses. The review above found experience didn't change accuracy much, and the habit makes your log more useful later.

Should I log RIR on warm-up sets?

No. It slows you down, and the numbers don't tell you anything useful.

08Sources

Checked November 10, 2026.

• Zourdos MC et al. (2016). Novel resistance training-specific rating of perceived exertion scale measuring repetitions in reserve. J Strength Cond Res. PubMed 26049792
• Halperin I et al. (2022, published online 2021). Accuracy in predicting repetitions to task failure in resistance exercise: a scoping review and exploratory meta-analysis. Sports Med. PubMed 34542869
• Refalo MC et al. (2023). Influence of resistance training proximity-to-failure on skeletal muscle hypertrophy: a systematic review with meta-analysis. Sports Med. PubMed 36334240
• Strong RPE and RIR mapping: Strong help center
• MacroFactor Workouts RIR: MacroFactor help center · App Store listing
• Hevy RPE logging: App Store listing
• Arrow rep-range progression: arrowfitnessapp.com · subscription and platforms: App Store listing