What is Reps in Reserve (RIR)?

What is Reps in Reserve (RIR)?

Reps in reserve is a simple way to rate how hard a set felt by estimating how many more clean reps you could have squeezed out before your muscles gave out. A set logged at 2 RIR means you stopped with roughly two good reps left in the tank; 0 RIR means you took the set to true failure. Because it's a direct rep count rather than an abstract 1-10 feeling, many lifters find RIR more intuitive to apply than RPE, even though the two describe the same underlying idea from opposite directions.

How it works

RIR works by asking you, immediately after a set, to estimate the gap between the reps you did and the reps you could have done with good form. That estimate lets you — or a program — set weights based on real-time effort rather than a fixed number on a spreadsheet: if last week's target of "3 RIR" actually felt like 1 RIR this week, you're more fatigued than expected and should hold or lower the weight rather than force a planned jump. RIR is essentially the mirror image of RPE — RPE rates effort on a 1-10 scale where 10 is hardest, while RIR counts reps left where 0 is hardest — and the same set can be described either way.

The scale

RIR and RPE describe the same effort scale from opposite ends — this is the RIR-first view of the scale used on the RPE page.

How to apply it

• Set a target RIR per exercise: Prescribe "squat 5 reps @ 2 RIR" instead of a fixed kg number, so the actual weight moves with how you feel that day.
• Rate your last set, not every set: Estimating RIR on your final 1-2 sets per exercise is usually enough to catch fatigue trends without over-tracking every rep.
• Calibrate against real failure occasionally: Take an exercise to true 0 RIR every few weeks so you have an accurate reference point for what 1-2 RIR actually feels like.
• Use it to taper or deload: Deliberately raising your target RIR (e.g. capping everything at 3-4 RIR) for a week is a simple, autoregulated way to deload.

Worked example

Say your program calls for "3 sets of 6 @ 2 RIR" on the bench press. Here's how that might play out across a training block.

The weight moves to hit the target RIR, not the other way around — the same autoregulation principle as RPE, described from the opposite direction.

Reps in reserve vs RPE

RIR and RPE are two labels for the same effort scale — most programs use them interchangeably, and some coaches cue both (e.g. "2 RIR / RPE 8") to reduce ambiguity.

By goal

• Beginners: RIR estimates are unreliable until you've experienced true failure a few times — start with fixed percentages or straightforward progression, then add RIR later.
• Intermediate/advanced lifters: Use RIR to autoregulate top sets so a bad-sleep or high-stress day doesn't force a grinding, high-risk set at a fixed weight.
• Powerlifters peaking for a meet: A planned rise in target RIR over the final weeks (an RIR-based taper) is a standard way to arrive at competition fresh.

Common misconceptions

• "RIR and RPE are different scales measuring different things." They describe the same underlying effort — RIR counts reps left (0 = failure), RPE rates it 1-10 (10 = failure) — just from opposite directions.
• "You should always aim for 0 RIR." Research shows most of the strength and hypertrophy benefit comes from training in the 1-4 RIR range; constant 0 RIR mainly adds fatigue without extra growth.
• "RIR estimates are too inaccurate to be useful." Estimation accuracy is lower far from failure and improves close to it, and improves further with training experience — even an imperfect RIR beats ignoring fatigue entirely.

Related terms

Reps in Reserve (RIR) FAQ

What does 2 RIR mean?

2 RIR means you stopped a set with about two clean reps left in reserve — the set was hard, but you could have completed roughly two more reps with good form if you had to.

Is RIR the same as RPE?

They describe the same effort scale from opposite ends: RIR counts reps left before failure, while RPE rates effort 1-10. 0 RIR equals RPE 10, 2 RIR equals RPE 8, and so on.

How accurate is reps in reserve?

Estimates are most accurate close to failure and less reliable when you're several reps away from it; accuracy also improves with training experience, similar to RPE.

Should beginners track RIR?

Beginners can start learning RIR, but estimates are unreliable until they've experienced true failure a few times. Most beginner programs use fixed weights or simple percentage progression first.

What RIR should I train at for muscle growth?

Most hypertrophy-focused programs target 1-4 RIR on working sets, occasionally pushing an isolation exercise to 0 RIR, since research shows similar growth across that range at equal volume.

Can RIR help me avoid injury?

Yes — training with 1-3 reps in reserve on technical lifts like squats and deadlifts helps preserve bar speed and form, reducing the breakdown that often happens right at true failure.

References

1. Zourdos MC, Klemp A, Dolan C, et al. Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve. J Strength Cond Res, 2016;30(1):267-75. PubMed 26049792
2. Helms ER, Cronin J, Storey A, Zourdos MC. Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training. Strength Cond J, 2016. PubMed 27531969
3. Bastos V, Machado S, Teixeira DS. Feasibility and Usefulness of Repetitions-In-Reserve Scales for Selecting Exercise Intensity: A Scoping Review. PMC11127506
4. Overshooting, Undershooting, Or Just Right? How To Perfect Your Ability To Predict Repetitions In Reserve. Stronger By Science