RIR at a glance
| Parameter | Value | Source |
|---|---|---|
| What you count | good reps left before muscular failure when you end the set | Refalo et al. 2023 |
| RIR and RPE | RPE 10 = RIR 0, RPE 9 = RIR 1, RPE 8 = RIR 2 | Zourdos et al. 2016 |
| Accuracy | you usually have 1 more rep left than it feels; calls are more accurate close to failure, in sets of up to 12 reps and in later sets | Halperin et al. 2022 |
| Enough effort | RIR 2-3 or a set close to failure | ACSM 2026 |
What RIR 0, RIR 1 and RIR 2 mean
You rate RIR at the end of a set: how many more good reps you could still do with the same weight. The table shows the levels from RIR 0 to RIR 4 and the matching RPE.
| RIR | RPE | What it feels like |
|---|---|---|
| 0 | 10 | Nothing left: the next rep would fail |
| 0.5 | 9.5 | Between RIR 0 and 1 |
| 1 | 9 | One more clean rep |
| 1.5 | 8.5 | Between RIR 1 and 2 |
| 2 | 8 | Two more clean reps |
| 2.5 | 7.5 | Between RIR 2 and 3 |
| 3 | 7 | Three left: moderate |
| 3.5 | 6.5 | Between RIR 3 and 4 |
| 4 | 6 | Easy: four or more left |
In SmartWorkout, RPE 6 to 10 in steps of 0.5 maps 1:1 to RIR 4 to 0. This simplifies the RIR-based RPE scale.
RIR 0
RIR 0 is the point where you cannot do another rep through the full range of motion without swinging. Research calls this muscular failure (Refalo et al. 2023); if you stop earlier because your form breaks down, that is technical failure, and you log it the same way, as RIR 0.
The moment you think you are done is often not failure yet: lifters with at least a year of training ended sets of leg extensions on average 2 reps before it (Armes et al. 2020). RIR 0 is optional: the 2026 ACSM position stand considers failure unnecessary for gains in strength, muscle size and power.
RIR 1
RIR 1 means one good rep is left when you end the set: the last rep is clearly slower, but your form holds. In the 8-week study by Refalo et al. 2024, the leg trained with 1-2 reps in reserve grew as much as the leg trained to failure, by about 0.18 cm of quadriceps thickness.
RIR 2
RIR 2 means you end the set with two good reps in reserve: the last rep slows down, but two more would go up. Among 42 trained lifters, one set at RIR 2 produced 8-week strength gains similar to those from one set to failure; some muscle measures came out slightly better with failure, but the differences were small (Hermann et al. 2025).
RIR 3, RIR 4 and half values
RIR 3 and 4 leave a bigger reserve, useful in a calibration week at the start of a plan and in a deload. Half values are for uncertain calls: RIR 1.5 means 1 or 2 were left. The further you are from failure, the less accurate your call, which is why Helms et al. 2016 merge levels 5-6 of the RPE scale into one description, “4-6 RIR”, and the table above stops at RIR 4.
How to use RIR for hypertrophy and strength
RIR measures effort, meaning how close to failure you end a set, while %1RM measures load; together they describe training intensity. Log RIR on every working set from your first workout, but base your progression on it only once your calls become accurate (Helms et al. 2016). From then on, RIR matches the load to how strong you are that day, which makes it a tool for autoregulation: on an off day the same RIR 2 comes at a lighter weight.
The ranges in the table are our practice.
| Situation | End the set at | Why |
|---|---|---|
| Hypertrophy: machines, cables, isolation | RIR 0-2 | failure is safe here, and muscles grow more the closer to failure you end your sets (Robinson et al. 2024) |
| Hypertrophy: heavy compound lifts | RIR 1-3 | misjudging your reserve has worse consequences here, and failure is not needed |
| Strength | RIR 1-3 | strength grows similarly across a wide RIR range (same Robinson et al. analysis) |
| First weeks of training | RIR 2-3 | the reserve leaves a margin for misjudged calls |
RIR describes the set, not the muscle. When your grip, your breathing or a helper muscle ends the set, as in rows or deadlifts, the target muscle usually has more in reserve than the RIR you log.
RIR works poorly in light, fast power sets below 80% 1RM (Helms et al. 2016), in warm-up sets and in timed exercises such as the plank.
How to learn to estimate RIR
- Pick an exercise you can safely take to failure, such as Machine Chest Fly, Seated Leg Extension Machine or Cable Triceps Pushdown. Do not test the barbell squat, the barbell bench press or the deadlift to failure.
- Before the set, predict the outcome, for example “10 reps, 2 left”.
- Do those 10 reps and keep going to failure.
- Compare: if 4 more reps go up after the tenth, your reserve was 2 reps bigger than you predicted.
- Adjust the load, following our practice: within the rep range, add reps first; at the top of the range, if your reserve was 2 reps bigger than predicted, add 5-8% (5-7.5 kg at 80 kg). The RIR/RPE calculator works out the exact weight for a target RIR.
- Repeat the test every few weeks; day to day, log RIR right after each working set.
Expect your calls in the first weeks to be off by 2-3 reps; that is normal, and it is why you run the test. Your first set is the hardest to call: in the study by Hackett et al. 2018 the error was 2 reps in the first set and 0.6 in the third, so adjust the load only after the second set. Accuracy can be trained: over 6 sessions in 6 weeks, the error of an “RIR 2” call on the leg press fell from 2.9 to 1.4 reps in younger adults (Wiedenmann et al. 2026).
How to tell how many reps you have left
During a set, the signals below give away how many reps you have left; this table is our practice. Speed is the most reliable signal, because the closer you are to failure, the slower the rep (Zourdos et al. 2016).
| Signal in the set | Usually left |
|---|---|
| first clearly slower rep | 1-3 reps |
| a rep stalls mid-range | 0-1 |
| a pause for breath between reps | 0-1 |
| form changes or the range of motion shrinks | 0, end the set |
| muscle burn, grimacing | tell you nothing about your reserve |
RIR examples set by set and week by week
An RIR call after a set tells you what to change next time, as these two examples show.
| Exercise | Plan target | Sets: weight × reps, RIR | Rest | What it tells you |
|---|---|---|---|---|
| Barbell Bench Press | 3 × 6-10 RIR 2 | 80 kg × 10, RIR 4; 80 kg × 10, RIR 3; 80 kg × 10, RIR 3 | 180 s | top of the range with more in reserve than the target, so by double progression you go to 85 kg next session |
| Machine Chest Fly | 2 × 10-15 RIR 1 and a test set | 45 kg × 12, RIR 1; 45 kg × 12, RIR 1; 45 kg × 15 to failure | 90 s | the fatigued third set still reached 15, so your “RIR 1” sets had at least 3 left: add weight |
In the free 8-week 4-day upper/lower plan for intermediates, week 1 is a calibration week with targets 1 RIR higher and week 8 is a deload at RIR 4. In weeks 2-7 we aim for RIR 1 on machines and cables and for RIR 2 on heavy compound lifts: if you misjudge your reserve on a machine and hit failure, nothing bad happens, while with a barbell the same miss can break your form.
- Free-weight compound lifts
- Machines, cables and isolation
Exercises for learning to judge RIR
For an RIR test, pick an exercise you can stop at any moment without risk.
| Good fit | Why |
|---|---|
| Machine Chest Fly | fixed path of motion, and you set the weight down safely |
| Seated Leg Extension Machine | isolation on a machine, so you never lose control of the weight |
| Cable Triceps Pushdown | isolation on a cable, and you can let the stack down without risk |
| Push-Up | failure is safe; pick a version where it comes quickly, for example with your feet elevated |
| No failure test | Why |
|---|---|
| Barbell Bench Press | failure leaves a loaded bar over your chest; stop at RIR 1-3, and your call is more accurate here than in the squat (Hermann et al. 2025) |
| Barbell Squat | failure leaves a loaded bar on your back; stop at RIR 1-3 |
| Deadlift | the last reps are the easiest to grind out with bad form; stop at RIR 2-3 |
RIR vs RPE, %1RM and failure
| RIR | RIR-based RPE | %1RM | Training to failure | |
|---|---|---|---|---|
| What it measures | good reps left at the end of the set | the same reserve on a scale to 10: RPE = 10 − RIR (Zourdos et al. 2016) | load as a percentage of your one-rep max | you end the set at RIR 0 |
| Written as | 3 × 8 RIR 2 | 3 × 8 RPE 8 | 3 × 8 at 75% 1RM | last set to failure |
| On an off day | load or reps go down, effort stays the same | same as RIR | load stays the same, the set ends closer to failure | always maximal effort |
Which scale to choose is covered in RIR vs RPE, and you can estimate your one-rep max from a set with RIR in the 1RM calculator.
Common RIR mistakes
- Ending sets too early. You often read that people overestimate their reserve. Research shows the opposite: you end sets earlier than you need to (Halperin et al. 2022). Run a failure test on a machine every few weeks.
- Trusting your call in long sets. In a squat set of about 16 reps, an “RPE 9” call was off by 2 reps on average (Zourdos et al. 2021). At 15 reps or more, assume 1-2 more reps in reserve than you feel.
- Failure on heavy compound lifts. For some people, older adults for example, failure may be unwise because of the injury risk when form breaks down (ACSM 2026). Save RIR 0 for machines and isolation exercises.
- Failure on every set. In a meta-analysis of 15 studies, training to failure did not build more muscle than stopping short of it (Refalo et al. 2023), and it is more fatiguing (Refalo et al. 2024). At most, take the last set of a safe exercise to failure.
What the research says about RIR
Research on RIR asks how accurately people judge their reserve and whether proximity to failure changes muscle and strength gains.
| Study | Type and sample | Result | Limitation |
|---|---|---|---|
| Halperin et al. 2022 | meta-analysis, 12 studies, 414 people | reserve underestimated by 0.95 reps on average; more accurate close to failure, at 12 reps or fewer and in later sets | results varied widely between studies (I² 97.9%) |
| Refalo et al. 2023 | meta-analysis, 15 studies | training to failure gave no more muscle growth than stopping short of failure | different definitions of failure |
| Robinson et al. 2024 | series of meta-regressions | muscle grows more the closer to failure; strength grows similarly across a wide RIR range | RIR estimated from study descriptions; exploratory analysis |
| The 2026 ACSM position stand | overview of reviews | 2-3 RIR or a set close to failure is enough effort | too little data for an exact target RIR |
| Refalo et al. 2024 | 18 trained people, 8 weeks; one leg to failure, the other at RIR 1-2 | result above; more fatigue after failure | small sample |
| Hermann et al. 2025 | 42 trained people, 1 set of 9 exercises, 8 weeks | result above; RIR calls improved, most in the bench press | one set per exercise |
| Wiedenmann et al. 2026 | 13 younger and 13 older adults, 6 sessions | result above; people saw their error only by going to failure, with no other feedback | small sample |
Whether an error of about 1 rep is acceptable remains unknown: the authors of the meta-analysis leave the question open, and a review of 31 studies (855 people) describes the samples as mostly adult men (Bastos et al. 2024).
What SmartWorkout logs show about RIR
Since you usually have more left than you feel, some of those RIR 0 sets still had reps in reserve. We convert sets logged in RPE to RIR (RIR = 10 − RPE), and we calculate every number in aggregate, from at least 50 people.
How to log RIR in SmartWorkout
You can log RIR in SmartWorkout on every working set: it is the default effort scale in the workout log, and in a plan it is also the target for each set.
- Open “Workout Settings” (the settings icon on the workout screen) and under “Effort scale” check that “Scale type” is set to RIR.
- During a workout, enter the reps for the set, tap “RIR” on the keyboard and pick a value from 0 to 4 (in 0.5 steps). The keyboard shows a description of the level, for example “You could have done 2 more repetitions.”
- In the plan creator, choose RIR as the “Load Indicator” and enter the target RIR for each set.
You log a set to failure as RIR 0, because there is no separate failure flag.
In Premium, suggestions for your next workout take your logged RIR into account, so the more often you log it, the better they can tell whether to add a rep or add weight (progression suggestions).
You can paste this plan fragment through plan import (Workout > My Plans > “+” > “Import plan”). It is a shortened Upper A day from the 4-day upper/lower plan, with the machine chest fly and a test set in place of the cable middle chest fly. Import costs 10 AI credits, so your welcome credits cover it.
DAY: Upper A- Barbell Bench Press | WU 2x5 | 3x6-10 RIR 2 | TEMPO 20X0 | REST 180- Barbell Bent Over Row | 3x6-10 RIR 2 | TEMPO 2010 | REST 150- Cable Lat Pulldown | 3x8-12 RIR 1 | TEMPO 2011 | REST 120- Machine Chest Fly | 2x10-15 RIR 1 + 1x10+ RIR 0 | TEMPO 2011 | REST 90How the effort scale works in the app is covered in the help article on logging RIR, RPE and tempo.
Log it in SmartWorkout
A free workout log for iPhone and Android: sets, RIR, tempo, exercise groups and plans.
Questions
What does 2 RIR feel like?
Your last rep slows down, but your form holds and you are sure two more would go up. If a rep stalls mid-range, you are already at RIR 0-1.
Is 0 RIR failure?
Yes. RIR 0 is the point where you cannot do another rep through the full range of motion without swinging. Research calls this muscular failure; if you stop earlier because your form breaks down, that is technical failure, and you log it the same way, as RIR 0.
Does 3 RIR build muscle?
Yes: the 2026 ACSM position stand counts 2-3 RIR as enough effort. Meta-regressions by Robinson et al. 2024 suggest, though, that muscles grow more the closer you get to failure, so on isolation exercises you can end sets at RIR 0-2.
What does RIR 2-3 mean in a workout plan?
Aim for 2 reps in reserve; if you end up with 3, the set still meets the target. The range leaves room for an off day and for a misjudged set.
How many RIR is RPE 7?
RPE 7 is RIR 3. On the RIR-based RPE scale, RPE = 10 − RIR, so RPE 8 is RIR 2 and RPE 10 is RIR 0; which of the two to use is covered in RIR vs RPE.
How do I know if my RIR is accurate?
Take a test set to failure on a machine or a cable and compare your rep count with your call. A difference of up to 1 rep is a good result: that is the average error in studies.
See also
- RPE scale for lifting: what it is and what RPE 8, 9 and 10 meanThe RPE scale (rating of perceived exertion) in strength training rates a set by the reps left in reserve: RPE 10 means none left, RPE 9 one and RPE 8 two. It is a different scale from the Borg scale used in endurance training, which rates overall exertion.
- Training to failure: when it helps and when it just adds fatigueTraining to failure means ending a set only when, despite full effort, you cannot complete the next rep through a full range of motion without changing your form. In a meta-analysis of 15 studies it built no significantly more muscle or strength than stopping short of failure, and it is clearly more fatiguing.
- Training intensity: percentage of 1RM vs proximity to failure and how to increase itTraining intensity has two meanings in lifting: load as a percentage of one-rep max (%1RM) and effort, meaning how close to failure a set ends (RIR). At 80% of 1RM lifters average about 9 reps to failure on the bench press and 13 on the leg press. Muscle grows from about 30% of 1RM when sets end close to failure.
- Progressive overload: what it is, linear vs double progression, and how to break a plateauProgressive overload is the gradual increase of training demands, most often load, reps or sets. The ACSM advises adding 2-10% load once you do 1-2 reps over your target in two sessions in a row. In an 8-week study, adding reps built about as much muscle as adding load.
- Rep ranges: how many reps for hypertrophy, strength and cuttingA rep range is the span of reps, such as 8-12, in which a set with a given weight should end. For muscle growth the exact number matters little: in studies, muscle grew similarly with sets of about 5 to more than 30 reps close to failure, while strength grew most with loads of 80% of 1RM or more.
- AMRAP: what it means and how to do an AMRAP set at the gymAn AMRAP set (as many reps as possible) is a set in which you do as many clean reps as you can with a given weight. Plans write it as “10+”: a minimum with no upper limit. In CrossFit the same abbreviation means a timed workout: as many rounds as possible, e.g. in 20 minutes.
- Deload week: what it means, how often to deload and how to do itA deload (deload week) is a planned period of lighter training, usually 5-7 days, that reduces fatigue before the next training block. Coaches cut the number of sets or reps by 30-50% and stop sets further from failure. In studies, neither a lighter week nor a week off reduced muscle growth.
- Top set and back-off sets: what they are and how much weight to dropA top set is the heaviest working set of an exercise in a session, and back-off sets are 2-4 working sets after it, done after full rest and usually 5-20% lighter. In a 6-week study of powerlifters, 2 back-off sets at 80% of the top set weight gave clearer strength gains than the top set alone.
Sources
- 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.
- Helms ER, Cronin J, Storey A, et al. Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training. Strength Cond J. 2016;38(4):42-49.
- Halperin I, Malleron T, Har-Nir I, et al. Accuracy in Predicting Repetitions to Task Failure in Resistance Exercise: A Scoping Review and Exploratory Meta-analysis. Sports Med. 2022;52(2):377-390 (online 2021).
- Hackett DA, Cobley SP, Halaki M. Estimation of Repetitions to Failure for Monitoring Resistance Exercise Intensity: Building a Case for Application. J Strength Cond Res. 2018;32(5):1352-1359.
- Zourdos MC, Goldsmith JA, Helms ER, et al. Proximity to Failure and Total Repetitions Performed in a Set Influences Accuracy of Intraset Repetitions in Reserve-Based Rating of Perceived Exertion. J Strength Cond Res. 2021;35(Suppl 1):S158-S165.
- Armes C, Standish-Hunt H, Androulakis-Korakakis P, et al. "Just One More Rep!" - Ability to Predict Proximity to Task Failure in Resistance Trained Persons. Front Psychol. 2020;11:565416.
- Wiedenmann T, Kunellis D, Rappelt L, et al. Trainability of repetitions-in-reserve estimation in younger and older adults: a parallel-group repeated-measures study. BMC Sports Sci Med Rehabil. 2026;18(1):375.
- Hermann T, Mohan AE, Enes A, et al. Without Fail: Muscular Adaptations in Single-Set Resistance Training Performed to Failure or with Repetitions-in-Reserve. Med Sci Sports Exerc. 2025;57(9):2021-2031.
- Bastos V, Machado S, Teixeira DS. Feasibility and Usefulness of Repetitions-In-Reserve Scales for Selecting Exercise Intensity: A Scoping Review. Percept Mot Skills. 2024;131(3):940-970.
- Refalo MC, Helms ER, Trexler ET, et al. Influence of Resistance Training Proximity-to-Failure on Skeletal Muscle Hypertrophy: A Systematic Review with Meta-analysis. Sports Med. 2023;53(3):649-665 (online 2022).
- Robinson ZP, Pelland JC, Remmert JF, et al. Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions. Sports Med. 2024;54(9):2209-2231.
- Refalo MC, Helms ER, Robinson ZP, et al. Similar muscle hypertrophy following eight weeks of resistance training to momentary muscular failure or with repetitions-in-reserve in resistance-trained individuals. J Sports Sci. 2024;42(1):85-101.
- Currier BS, D'Souza AC, Singh MAF, et al. American College of Sports Medicine Position Stand. Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews. Med Sci Sports Exerc. 2026;58(4):851-872.