What Is RIR in Lifting? Meaning, RIR–RPE Chart and How to Use It

RIR (reps in reserve) is the number of reps you could still have done when you end a set. If you bench press 8 reps and think you had 10 in you, that set was at RIR 2.

It measures how hard you train without relying on the weight alone. The same 80 kg can feel easy one day and close to failure the next, depending on sleep or food. RIR captures that real effort.

What each RIR value means

RIR	RPE	What it means	When it's used
0	10	Failure: not one more rep	Last set, isolation exercises
1	9	One rep left	Hard hypertrophy sets
2	8	Two reps left	Typical hypertrophy work
3	7	Three reps left	Heavy compound lifts, early weeks
4+	6 or less	Comfortable set	Warm-ups, deload weeks

The RPE column is another way of saying the same thing. The resistance-training RPE scale (Zourdos et al., 2016) defines RPE 10 as zero reps in reserve, RPE 9 as one, and so on: RIR = 10 − RPE.

Why RIR matters for muscle growth

For a muscle to grow, the set has to be challenging. RIR is the most practical way to tell whether it was.

What the research says:

• The closer to failure, the more growth. A 2024 analysis pooling the available studies found that muscle size gains improved as sets ended closer to failure. Strength was different: RIR barely mattered, with similar gains across a wide range (Robinson et al., 2024).
• But failure itself isn't better than getting close. A 2022 meta-analysis found no hypertrophy advantage for training to momentary muscular failure over stopping short (Refalo et al., 2022). The authors point to a possible non-linear relationship: past a certain point, getting even closer to failure doesn't always add more.

That's why the most common practical advice is to keep most sets between RIR 0 and RIR 3. Close enough to failure for the stimulus to count, without piling up the fatigue that comes from always going to the limit.

Which RIR to use for each exercise

A common guideline among coaches, not a fixed rule:

• Heavy compound lifts (squat, deadlift, bench press, barbell row): RIR 1–3. Failure on these is very fatiguing, takes longer to recover from, and form breaks down exactly when the load is heaviest.
• Isolation and machines (biceps curls, extensions, lateral raises): RIR 0–2. Failure here is safe and barely tires the rest of the body.
• Across a mesocycle: it's common to start at RIR 3 in the first weeks and work down to RIR 0–1 by the end, before a deload week.

How to estimate your RIR (and why you'll be off at first)

Estimating RIR is a skill, and almost nobody has it from day one. A meta-analysis on how accurate these estimates are found that people underpredict by almost one rep on average: they think they're closer to failure than they really are (Halperin et al., 2021).

The same paper gives three useful clues:

1. Estimates are better close to failure. Saying "one left" is easier than saying "five left".
2. Estimates are better with heavier loads. Sets of 12 reps or fewer are judged noticeably better than long sets.
3. Estimates are better in later sets of the exercise.

To sharpen it:

• Calibrate now and then. On a safe exercise (a machine, or with a spotter), estimate your RIR at a given rep and then keep going to failure. The difference tells you how far off you are.
• Log RIR on every set. If you always write it down, you see how it changes week to week and learn to recognise what "two left" feels like.
• Watch the bar speed. When the bar starts moving clearly slower, you're often 2–3 reps from failure; treat it as a guide, not a rule. In Zourdos' study, the slower the bar moved, the higher the perceived effort.

RIR and double progression

RIR also tells you when to add weight. If your program calls for 8–10 reps at RIR 2 and you're already getting 10 reps with two left in the tank, the load is too light: time to go up.

If you hit failure before 8 reps with the same weight, keep the load until the reps come back.

How MUTARA tracks RIR

In MUTARA every exercise in your routine has a target RIR (for example, "4 sets × 6–10 reps · RIR 1–2"), and every set is logged with its weight, reps and RIR. With that data the app suggests the weight for your next session: go up, hold or go down, depending on whether you hit the target.

No maths, no trying to remember what you did last week. Just be honest about your RIR.