RIR and RPE explained: how hard should you train?

What does RIR mean?

RIR means repetitions in reserve. It is an estimate of how many more complete repetitions you believe you could perform before reaching momentary muscular failure.

If you finish a set and believe you could complete roughly three more good repetitions as prescribed, you would record about 3 RIR.

At 0 RIR, no further complete repetition can be performed through the prescribed range of motion with the required form. That is the failure point the scale counts towards.

RIR describes your estimate at the end of that set. It does not measure effort directly, and it does not guarantee that the estimate is correct.

What does RPE mean in weight training?

RPE means rating of perceived exertion. In this guide, it refers specifically to the resistance-training RIR-based RPE scale used to rate the effort of an individual set.

On this scale, RPE 10 is maximal effort with no further complete repetition possible. RPE 9 means about one good repetition remained, and RPE 8 means about two remained.

This is not the same as generic exercise RPE, session RPE, the Borg 6–20 scale or the Borg CR10 scale. Those tools use perceived exertion in different ways and should not be mixed with this resistance-training scale.

RPE and RIR table

The top of the resistance-training scale uses clear repetitions-in-reserve anchors. Farther from failure, an exact rep-count conversion becomes less useful and less precise.

Treat the table as a set of practical anchors. It is not a universal promise that subtracting RIR from 10 produces a precise RPE at every point for every person and exercise.

Why RPE and RIR move in opposite directions

RIR counts what is believed to remain, so the number falls as the set gets harder.

RPE rates how demanding the set was, so the number rises as the set gets harder.

A set ending at about 3 RIR is less demanding than one ending at 1 RIR. On the resistance-training scale, those estimates correspond approximately to RPE 7 and RPE 9.

The inverse relationship is easiest to interpret near failure, where the upper anchors are clearest. It should not be treated as a perfectly precise conversion across the whole scale.

Why use RIR or RPE at all?

Repetitions and load tell you what work was performed. RIR or RPE adds an estimate of how demanding that work was on that day.

That can help you distinguish an easy set from a genuinely challenging one, even when both contain the same exercise, load and repetition count.

It can also help a programme describe intended effort without pretending that everyone can perform the same repetitions with the same percentage of a previous maximum.

The rating is supporting information alongside technique, recovery and progressing repetitions or load over time. It is not a replacement for those records.

Are RIR and RPE objective measurements?

No. They are subjective estimates based on what you believe you could still do.

Unlike load on the bar or repetitions completed, the repetitions that remained were not actually performed. The estimate can be influenced by experience, exercise familiarity, motivation, discomfort and how clearly failure has been defined.

That does not make the tools useless. It means their value comes from consistent use, honest recording and interpretation alongside objective training performance.

Are beginners good at estimating RIR?

Beginners should not expect perfect estimates. They have fewer completed sets and fewer true reference points for judging how many repetitions genuinely remained.

Estimates also tend to be more meaningful near failure than when many repetitions remain. Saying that a set was approximately 1 or 2 RIR is more useful than claiming an easy set was exactly 7 RIR.

Beginners can still use the tool. The right attitude is to treat early ratings as estimates that improve with practice.

Do you need to reach 0 RIR?

No. Every working set does not need to reach 0 RIR.

Current evidence does not show that training to momentary muscular failure is required or consistently superior for hypertrophy.

That conclusion does not make effort irrelevant. A set stopped with many easy repetitions available is not necessarily equivalent to a set that becomes genuinely challenging.

Is 2 RIR better than 3 RIR?

Research has not established one universally optimal RIR for every set, exercise, person and goal.

Two RIR and three RIR are neighbouring subjective estimates, not sharply separate biological zones. The difference may also be smaller than the person’s estimation error.

A programme can still use a target such as about 2 RIR to communicate that a set should be challenging without deliberately reaching failure. That is a practical instruction, not proof that 2 RIR is universally better than 3 RIR.

Use the target consistently enough to learn from your performance rather than changing it every session in search of a perfect number.

A practical beginner example

Imagine your programme prescribes a chest press for 3 sets of 8–12 repetitions at about 2 RIR.

The falling repetition count does not automatically mean the later sets failed. Fatigue can make the same load more demanding, so the final set may finish closer to failure even with fewer repetitions.

Exact perfection is not required. If the first set was really 3 RIR or the final set was closer to 2 RIR, the record can still help you understand the session and make a sensible next decision.

Should you use RPE or RIR?

Either can work when everyone involved understands which scale is being used.

RIR asks a direct question: how many good repetitions did you believe remained? Some beginners find that easier to understand than converting the estimate into an RPE number.

The resistance-training RPE scale can be convenient when a programme already uses RPE targets. Its upper anchors carry the same information in the opposite direction: RPE 10 is about 0 RIR, RPE 9 about 1 RIR and RPE 8 about 2 RIR.

Choose one language, learn it and record it consistently. Do not switch between unrelated RPE scales.

How to get better at estimating effort

Build the skill gradually rather than trying to prove every estimate by reaching failure.

• use the same definition of a complete repetition each time
• record the load, repetitions and estimated RIR or RPE after the set
• compare estimates with how repetitions and technique changed across later sets
• keep exercise setup and range of motion consistent
• review patterns over several sessions rather than judging one rating in isolation
• treat estimates farther from failure as broad descriptions rather than exact counts

Occasional appropriately supervised calibration may help an experienced lifter understand the upper anchors, but every set does not need to become a failure test.

Common RIR and RPE mistakes

• treating RPE or RIR as an objective measurement
• assuming RPE 8 guarantees exactly two repetitions for everyone
• thinking every set must reach 0 RIR
• calling an easy set 2 RIR because the programme says so
• mixing generic or cardio RPE with resistance-training RIR-based RPE
• changing targets constantly
• ignoring technique and progression while obsessing over the number

The scales are useful when they clarify training. If the number becomes more important than honest effort, controlled repetitions and recorded progress, it has stopped serving its purpose.

The practical takeaway

RIR counts down as momentary muscular failure approaches. Resistance-training RPE goes up.

RPE 10 is approximately 0 RIR, RPE 9 approximately 1 RIR and RPE 8 approximately 2 RIR.

They are subjective estimates, not objective measurements or a perfectly exact conversion across the whole scale.

You do not need to reach 0 RIR on every set, and research has not established one universally optimal RIR.

For a beginner, their best use is learning the difference between an easy set and a genuinely challenging one while also paying attention to repetitions, load, technique, recovery and progress.