RIR Meaning in the Gym: What Reps in Reserve Is, With a Chart
RIR stands for reps in reserve — how many more reps you could have done before failure. What 0-3 RIR mean, the RIR-RPE chart, and how to use it in lifting.
Riven · TrainingRIR means "reps in reserve" — the number of extra reps you could still have done, with good form, at the moment you ended a set. Stop at 10 reps when you could have ground out 12, and that set was 2 RIR. 0 RIR means you hit failure: the next rep would not have moved. That's the whole definition. The rest of this page is the chart, what each number feels like, and the one thing nobody tells beginners — that your RIR guess is probably off by a couple of reps.
A quick gym scene to make it stick. Two lifters bench 80 kg for 8. One racks it breathing easy, bar speed unchanged — that was 4 or 5 RIR. The other's last rep crawled and her elbows wobbled — that was 1 RIR. Same weight, same reps, completely different sets. RIR is the number that tells them apart.
What does RIR stand for?
RIR stands for reps in reserve. It comes from the resistance-training RPE scale built by Zourdos and colleagues (2016), where each RPE number is defined by how many reps you had left: RPE 10 is 0 RIR, RPE 9 is 1 RIR, RPE 8 is 2 RIR, and so on down to RPE 5 at about 5 RIR. So RIR isn't a separate system — it's the reps-remaining reading of the same effort scale. Coaches say "leave 2 in the tank", programs say "3 sets at 2 RIR", apps ask you to rate RIR after a set. All of them mean the same thing: how many reps short of failure did you stop?
What do 0, 1, 2 and 3 RIR mean?
Each RIR number is a distance from failure, and each has a distinct feel. Here is the chart I give every new client, with the RPE equivalent:
| RIR | RPE | What it means | What it feels like |
|---|---|---|---|
| 0 | 10 | True failure — you tried another rep and it didn't go | Last rep crawled; form breaking; nothing left |
| 1 | 9 | One more rep was possible, probably ugly | Last rep slow and grindy; one more would be a fight |
| 2 | 8 | Two clean reps left | Last rep clearly slower than the first; you could do two, not three |
| 3 | 7 | Three reps left | Bar slowing a little; honest work, far from the edge |
| 4 | 6 | Four reps left | Barely slowing; feels like a hard warm-up |
| 5 | 5 | Five or more left | Speed untouched; nobody can count past this |
Two things to notice. First, the scale stops being meaningful past about 5 RIR — once you have six-plus reps left, no one can count them, which is why the validated scale runs RIR 0-5 and not beyond. Second, the single best cue in the right-hand column is bar speed: 3 RIR and 1 RIR differ mostly in how much the last reps slowed down, and that is the cue your body reports least reliably.
RIR vs RPE in one sentence
RPE asks "how hard was that?" on a 1-10 scale; RIR asks "how many reps were left?" and gives a count — and on the modern lifting scale they are the same measurement read two ways (RPE 8 = 2 RIR). I prefer RIR for coaching because "two reps left" is checkable and "felt like an 8" is not. The longer comparison, including when RPE is the better tool, is in RIR vs RPE.
How many RIR for hypertrophy vs strength?
For muscle growth, train most working sets at 0-3 RIR; for strength, you can sit further back, around 2-4 RIR, and keep most of the gains. That split comes straight from the research. The 2024 dose-response meta-regression by Robinson and colleagues concluded: "Strength gains were similar across a wide range of RIR, while muscle hypertrophy improves as sets are terminated closer to failure." And you don't need to reach 0 RIR: in Refalo and colleagues' 2024 trial, eight weeks at 1-2 RIR grew the quads 0.182 cm versus 0.181 cm for training to failure — identical growth, less fatigue. The goal-by-goal targets are laid out in how close to failure should you train.
Why your RIR is probably off
Most lifters misjudge RIR, and the error runs the same direction: they think they're closer to failure than they are. In Halperin and colleagues' (2020) experiments, trained lifters who stopped at what felt like failure actually had about two reps left on average. Beginners are worse — "2 RIR" is often really 4-5. Your sense of effort arrives before your muscle actually runs out, and it gets fuzzier the farther from failure you are. The full account of that error is in why your reps-in-reserve estimate is wrong, and the long-form guide is reps in reserve explained.
Can you measure RIR instead of guessing?
Partly, yes — through rep speed. As a muscle fatigues, the bar (and your wrist) slows, and that slowdown tracks proximity to failure: across sets, velocity loss runs roughly 25% at failure, 13% at 1 RIR and 8% at 3 RIR in Refalo and colleagues' review. Rep speed is the one cue in the chart above you can check from outside your own head, which makes it the objective second opinion for the moment your "2 RIR" and your last rep's speed disagree.
Riven is the Apple Watch app that scores muscle failure. It reads your wrist motion and stays quiet during the set; about three seconds after you rack the weight you get the exercise, the rep count and a 0-100 score. Reps slow down as a muscle nears failure, and that is what the score is built on. No barbell clip, no camera, no extra hardware. It shows you which set was the real one.
The three-method protocol — velocity, self-rating, and an occasional all-out set — is in how to measure reps in reserve, and the wrist-side evidence is in can the Apple Watch detect muscle failure.
How to use RIR this week
- Pick a target, not a weight. Write "3 x 8 at 2 RIR" instead of "3 x 8 at 60 kg", and let the load move to hit the target.
- Rate every set right after you rack it. Ask one question: how many more clean reps? Log the number.
- Calibrate once. Take one safe machine set to true 0 RIR and count how many reps came after the point you felt done. That gap is your personal correction.
- Watch the last two reps' speed. If they didn't slow, you were at 4+ RIR no matter what it felt like.
FAQ
What does RIR mean in the gym?
RIR means reps in reserve: how many more good reps you could have done before failure when you stopped the set. 0 RIR is failure, 2 RIR is two reps short.
Is 2 RIR hard?
Yes — 2 RIR is a genuinely hard set (RPE 8): the last rep is clearly slower than the first and you could do two more, not three. It's the most common hypertrophy target because it builds muscle about as well as failure with less fatigue.
What is 0 RIR?
0 RIR is true muscular failure — you attempted another rep and could not complete it with good form. It equals RPE 10.
What does 3 RIR mean?
3 RIR means you racked the weight with three clean reps still in you — RPE 7. The bar is slowing a little on the last rep but you are well short of the edge. It is honest work on a heavy compound lift and the far end of the 0-3 RIR range that grows muscle.
What is the difference between RIR and RPE?
They're two readings of the same effort scale. RPE rates how hard the set was (1-10); RIR counts the reps left. RPE 10 = 0 RIR, RPE 9 = 1 RIR, RPE 8 = 2 RIR.
How many RIR should I train at?
For muscle growth, most sets at 0-3 RIR; for strength, 2-4 RIR keeps most of the gains with less fatigue. Research shows 1-2 RIR grows muscle as well as going to failure.
Can an Apple Watch measure RIR?
Not RIR as a number, but it can read the thing RIR is guessing at: reps slow down as a muscle nears failure, and a device on your wrist can pick up that slowdown. Riven is the Apple Watch app that scores muscle failure; it scores each set the moment you rack it.
Sources
- Zourdos et al. (2016), Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve, J Strength Cond Res — https://pubmed.ncbi.nlm.nih.gov/26049792/
- Halperin et al. (2020), Just One More Rep: Ability to Predict Proximity to Task Failure in Resistance Trained Persons, Frontiers in Psychology — https://pmc.ncbi.nlm.nih.gov/articles/PMC7785525/
- Robinson, Pelland, Remmert, Refalo, Jukic, Steele & Zourdos (2024), Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions, Sports Medicine — https://pubmed.ncbi.nlm.nih.gov/38970765/
- Refalo et al. (2024), Similar muscle hypertrophy following eight weeks of resistance training to momentary muscular failure or with repetitions-in-reserve in resistance-trained individuals, Journal of Sports Sciences — https://pubmed.ncbi.nlm.nih.gov/38393985/
- Refalo et al. (2023), Influence of Resistance Training Proximity-to-Failure, Determined by Repetitions-in-Reserve, on Neuromuscular Fatigue in Resistance-Trained Males and Females, Sports Medicine - Open — https://pmc.ncbi.nlm.nih.gov/articles/PMC9908800/