Effective training programs rely on systems and a shared language of measurement. Without clear standards, you’re essentially guessing at your progress.
Reps in Reserve (RIR) is a vital part of that vocabulary. It’s a system designed to help you better understand the intensity of your training by measuring how close a set was to failure. By mastering this tool, you can move past guesswork and start regulating your training with more precision.
Let’s dive in.
A brief history of Reps in Reserve (RIR)
We’ll begin with a few definitions and explain where these systems came from and what they have in common.
The two most common terms in this conversation are:
Reps in Reserve (RIR): An estimate of how many reps you can perform before reaching failure. A typical example is if you are performing a barbell back squat and stop because you believe you have 2 reps remaining. That set would be rated as 2 RIR.
Rating of Perceived Exertion (RPE): A scale you can use to rate or describe how easy or difficult your effort feels. The starting and end points of these scales can vary, but generally in resistance training they work on a 1-10 scale, with 1 being the easiest and 10 being the hardest in terms of perceived effort.
A brief note on where these scales came from
We will talk in a moment about the importance of measurement in research methods, but when discussing RIR and RPE specifically, we’ll look to classic research from Gunnar Borg. He initially developed an RPE scale to help estimate the relationship between aerobic work and heart rate intensity. The original scale ranged from 6-20, and the numbers were designed to correspond to heart rate during exercise. For example, an RPE of 13 would roughly correspond to a heart rate of about 130 beats per minute, while an RPE of 20 would correlate with a heart rate of about 200 beats per minute, and so on.
He created variations of the scale over the years, but the core idea remained the same. It was a practical way to estimate how hard someone was working, and whether the effort represented a moderate, heavy, or near maximal level of exertion.
Again, these scales have their basis in aerobic exercise. For resistance training, Thomas DeLorme began refining a system in the 1940s while working with rehabilitation patients. It became a foundation for using repetition maximum and percentage-based training. By the late 1980s, prescribing loads using a percentage of one-repetition maximum (1RM) had become pretty standard in both research and programming as a way to measure and control intensity.
With 1RM, you’re essentially working from a percentage of the maximum amount of weight you can lift for a single repetition, usually within the boundaries of proper form (though this can be debated). Once you know what your maximum is, you would then design your programming around the percentage of those numbers.
| Standard percentage of 1RM table | ||
| Percentage of 1RM | Typical reps to failure | General intensity description |
| 100% | 1 | Maximal strength |
| 95% | 2 | Very heavy |
| 90% | 3–4 | Very heavy |
| 85% | 5–6 | Heavy |
| 80% | 7–8 | Heavy |
| 75% | 9–10 | Moderately heavy |
| 70% | 11–12 | Moderate |
| 65% | 13–15 | Moderate |
| 60% | 16–20 | Light |
| 55% or less | 20+ | Very light |
RIR is a relatively new system of measurement developed by Mike Tuchscherer in his Reactive Training Systems manual. RIR has been examined in research alongside measures like bar velocity. The current iteration of RIR typically stands on its own and uses a numbering system similar to an RPE-type score. RIR helps you understand reps left in reserve and the intensity of a set. However, accuracy tends to decrease when you’re estimating very high numbers of repetitions.
| RPE to RIR scale of effort | ||
| RPE score | Reps in reserve (RIR) | General description |
| 10 | 0 | Maximal effort, failure |
| 9.5 | 0–1 | Near maximal |
| 9 | 1 | Very hard |
| 8.5 | 1–2 | Hard |
| 8 | 2 | Challenging |
| 7.5 | 2–3 | Moderately hard |
| 7 | 3 | Moderate |
| 6 | 4 | Somewhat easy |
| 5 | 5–6 | Easy |
| Adapted from Zourdos et al (2016) | ||
To be clear, there isn’t a gold standard for estimating training intensity or one’s proximity to failure. Typically, reference methods default to a percentage of 1RM, but that approach also has its limitations. Ideally, what you are looking for in any estimation method is one that allows you to create a consistent testing system and clearly understand your reference points to your performance.
What does the research say about RIR?
If a research subject says they believe they have 2 reps left in reserve, but they continue the set to failure, were they right? If they are wrong, do they tend to be wrong by underestimating or overestimating their abilities? Are they staying within a reasonable range? In this instance, let’s first take a look at accuracy.
To answer those questions, we can look at a scoping review with an exploratory meta-analysis from Halperin et al that included 12 studies and 414 participants. Researchers examined how accurately people could predict the repetitions they had left before reaching failure across multiple resistance training studies. They found that participants tended to underestimate their repetitions to failure by roughly 1 rep on average. But for the most part, people were close enough to their true limit when compared with their estimations.
A few things to note: prediction accuracy improved as individuals got closer to failure, and accuracy also improved slightly as sets progressed compared with the first set.
In a study with male and female resistance-trained individuals, researchers looked at the accuracy of intra-set RIR predictions during the bench press. They essentially wanted to know whether lifters could correctly determine how many repetitions they had left before reaching failure. They found that the lifters did a pretty good job staying within about 1 rep of their failure range. It is also worth noting that the lifters had prior experience using RIR, so there is a strong chance that being familiar with the system helped.
A more recent 2025 study in older adults (average age about 68 years) with some resistance training experience found they had a tendency to underestimate their ability to perform additional repetitions. However, even with this reduced prediction accuracy, RIR appeared to function in a helpful way for guiding their training effort and volume.
Regarding validity, research suggests that RIR, while subjective, can be evaluated by comparing estimates to performance markers such as velocity. For example, studies have looked at the relationship between bar speed and proximity to failure. As we get closer to failure, bar speed tends to slow down. This relationship gives researchers a reference point for evaluating RIR estimates.
We talked a little about this pattern earlier in work from Zourdos et al. More recently, a study from Kraft et al in 2026 examined hang cleans across multiple sets and intensities, in which velocity at a given RIR remained relatively stable. In other words, when lifters report that they are close to failure, their bar speed usually reflects that change in effort. This can help support the use of RIR for these types of estimates.
Is working within a range instead of training to failure as effective? Are there benefits or downsides?
The balance between managing fatigue and reaching failure is complex. RIR is a strategic tool that can help you trend toward failure, allowing for high intensity even when a set isn’t taken to a total grind. If you are staying within that range close to failure, you are likely to see meaningful progress. This will obviously be affected by age, training status, and even the type of exercise you’re doing.
A 2025 study from Hermann et al examined muscular adaptations in single-set resistance training in both men and women. Participants either performed sets to failure or stopped within roughly 2 reps in reserve. The experiment lasted 8 weeks, with 2 sessions per week and 9 exercises per session. Researchers measured strength, power, muscle size, and endurance.
In the end, both groups improved across all outcomes. There were small trends that favored training to failure for muscle size and power, but the overall differences between groups were modest. This lines up with a meta-regression from Robinson et al that showed a small dose-response relationship with muscle growth, where training closer to failure was associated with slightly greater hypertrophy.
In practical terms, the analysis suggests that if training to failure led to about a 9% increase in muscle size, stopping with 1 to 2 reps in reserve might produce roughly an 8 to 8.5% increase. Strength outcomes were largely similar across a range of RIR values.
Another study from Refalo et al looked at how people felt (specifically, their perceived discomfort and perceived effort) when training to failure versus working at roughly 1 to 2 RIR. The results were fairly similar, and there wasn’t a large difference in outcomes.
However, when analyzing perceived discomfort, participants indicated a slight preference for working within RIR versus working to failure. If you struggle with sticking to your lifting routine, experimenting with more RIR-based training and less failure-based training may be worth considering.
Lastly, a meta-analysis and systematic review from Grgic et al compared training to failure with non-failure training. The authors stated that while training to failure is not necessarily harmful, it may not always be needed for progress, and that training close to failure appears to be sufficient for most strength and muscle outcomes.
Takeaways from this section: Once you’re accustomed to using RIR, it can serve as a decently accurate method for estimating effort, increasing intensity in your training, and gaining a better understanding of what failure feels like. While you don’t have to train to failure to see good results, there is something to be said for knowing where failure is and understanding your proximity to it. RIR isn’t perfect, but for estimation purposes and for consistently hitting a targeted range, it does a good enough job.
Establishing reference points
Now that we understand what RIR is and have reviewed the research on its use, let’s take a moment to understand why having a consistent reference point for measurement is actually useful in practice.
Imagine you’re trying out a new exercise at the gym. You pick a weight that intuitively seems “heavy enough,” but you aren’t quite sure. You might be able to get a good workout or two this way. But over time, it becomes more difficult to measure your progress and know if you’re truly reaching your potential. That’s where a system like RIR comes in handy.
The importance of anchoring the scale
In research, the term “anchoring” appears in statistical and psychology literature as a method for calibration and improving consistency in measurement. While anchoring does not eliminate bias entirely, the goal is to improve a person’s reference points so their judgments become more reliable.
Let’s start with a simple visualization exercise.
If I asked 100 people, without any basis or training, how many parked cars could fit on a football field, the range of answers would likely be very wide. Someone might know that a football field is 100 yards long (120 if including the end zones), but have no clear sense of the field’s width (53 yards) or the space an average car occupies (roughly 14 feet depending on the vehicle). Not to mention, the question itself contains many variables, such as the spacing between cars or the layout. With so much uncertainty, estimates will have wide ranges.
However, if I provided those same individuals a picture showing one horizontal and one vertical row of cars on the field, there would likely be an immediate and noticeable improvement in their guesses. If I then showed half of the field filled with cars, the estimates would likely improve again. As more of the unknown space is replaced with visible reference points, people will have less to guess about. The results would not be perfectly accurate, but they would likely move closer to the true value.
With RIR, you are dealing with something pretty complex: a person’s rating tied to their beliefs about their physical effort and fatigue. One person’s estimate of 2 RIR might reflect stopping with several repetitions still available, while another person’s estimate might be much closer to the actual limit.
So what’s the solution? In this instance, it’s exposure to true failure, which helps anchor the scale.
We need a safe way to evaluate each individual’s endpoint reference so they can begin estimating effort relative to it. Once a clear reference exists, individuals can work backward from that endpoint when judging how many repetitions remain.
How to make meaningful starting estimates
If you aren’t comfortable making starting estimates for testing failure (or you are venturing into a new lift that aren’t comfortable with), I’ve provided step-by-step instructions below.
If you are already comfortable taking a guess or estimate to test true failure, you can skip to the next section.
Step 1: Pick a stable exercise and focus on the movement first
I’m a fan of starting with more stable movements when you are learning how to test your limits. When the movement is well-supported and stable, it can be easier to control the set. So, the goal is to choose an exercise where the risk of losing control is lower.
For example, if you are new to training and decide to test failure with a lateral raise, you could run into problems quickly. Smaller muscle groups and less stable movements can fatigue quickly, and form may break down before you have a clear sense of your limit. Instead, when new to testing RIR, look for movements that are more stable and easy to stop when fatigue builds.
Good exercises for testing RIR when beginning training:
Dumbbell box or bench squats
Seated cable rows
Neutral grip dumbbell bench press
Lat pulldown
Dumbbell bicep curls
Cable triceps pushdowns
Step 2: Warm up with light weight and a repeatable moderate load
Take the time to get comfortable with the movement and feel out how much strength and how many repetitions you have available on that day. Start with a light weight and increase the load over a few sets, and pay attention to how your form holds or changes as fatigue sets in with each rep. Keep in mind that endurance fatigue can become its own limiting factor, so typically you’ll want to keep most warm-up sets under about 12 reps and well short of failure.
During your warm-up, feel free to adjust the weight and increase gradually as you test the movement. Unless you notice you are very far from the target range, resist making big jumps in weight during the warm-up.
Lastly, don’t neglect rest if you feel you got closer to failure than you meant to during a warm-up set.
The goal of the warm-up sets is to hone in on a solid first working set estimate and gauge how close you are to failure by the time you hit your last set. Based on these warm-up sets, you should have a reasonable idea of a weight that will place you within a useful range for testing true failure.
Testing true failure and RIR estimates
Now we are assuming that you have a decent understanding of the exercise you want to perform and have a meaningful starting estimate. From here, you can start to get an anchor for your scale.
Quick note on what defines failure
For our purposes here, we’ll define “failure” as the following:
Failure – The point at which the lifter can no longer complete a repetition in proper technical form for the exercise.
This can, but does not always, coincide with momentary muscular failure. Technical failure and momentary muscular failure can be the same, but they are not always identical. Safety should be the priority, and there are times when you can feel that the last completed rep started to show failure components, such as losing form, so you do not need to attempt another rep to know it would result in failure. The difference between these two points is usually small, so go with safety and what feels best within this range.
Step 1: Select your exercise and choose a weight with a repeatable load
You should select a weight where you expect to reach failure somewhere within the range of 6-12 repetitions. The most important aspect of this test is to ask yourself: How many reps can I do with this weight before failure?
For example, let’s say you are performing a seated cable row test, and based on warm-ups and estimates, you think you can lift 80lb for about 10 reps before reaching failure. That’s your estimate.
Step 2: Perform the set and test your RIR estimate
You will now perform the seated cable rows while trying to reach failure, keeping in mind ideal form and technique. This is important because you do not want to achieve reps by, for example, rounding your shoulders or jerking the cable and breaking down in form. All 10 reps should ideally be performed with proper technique and show muscular fatigue taking place, not just mental fatigue or boredom with the movement.
Note: If the movement produces a sharp pain, you should stop. But if you are simply feeling mentally uncomfortable or tired of the effort, that is not the type of failure we are describing here.
Continue the set until you can no longer complete another repetition with proper technique, despite trying. As a reminder, in this example we estimated that using 80lb would fail rep 10. You should, if your estimate is correct, fail to complete rep 11 or not attempt an 11th rep due to how your 10th rep went.
Result of your test? You actually reached 12 reps before failure. You now know that, at this stage of your testing, 80lb performed for 10 reps would represent about a 2 RIR, and that your original estimate was slightly off.
Do not worry about being perfect with your estimate. Be more concerned with maintaining good form and noting where you actually are in your RIR range.
Step 3: Continue testing different exercises and building your RIR judgment
Depending on the exercise selection, training experience, or training session, you may not want to take every exercise to failure in one session. This is largely a matter of judgment and should take into account your current nutrition, recovery, and conditioning.
In short, if you feel well-rested, well-fed, and ready to test, then proceed. If you feel that testing the seated row to failure might negatively affect your lat pulldown later, simply wait until your next workout to test again.
Understand that this is a conservative approach and assumes a little less experience. If you are just getting back into training, it can be wise to lean toward the conservative side to manage fatigue. If you have been training for a while but have never formally tested your limits, you can likely push your limits a little more.
Step 4: Apply RIR to your regular sets
Now that you understand anchoring and where failure occurs, you can start dialing back and aim to hit the target RIR range within your sets, if your program calls for it.
For example, let’s say you are training seated rows and your target is 2 RIR for each set. From previous testing, you now know that 80lb left you with roughly 2 reps in reserve during testing. That gives you a starting point.
From here, the goal is to build a general sense of where 1 RIR, 2 RIR, or failure occurs across the exercises in your program so that you can make more confident estimates during training.
Step 5: Periodically retest to keep your RIR estimates updated
Over time, you should test those estimates by occasionally performing a set-to-failure test. How often varies for each person and depends largely on your fatigue management and recovery. Some people test their last set at the end of most sessions, while others rotate and test a different exercise each session or only at the beginning of each cycle.
When deciding whether it is time to test again, ask yourself a few simple questions:
- Are you performing a new exercise or using unfamiliar equipment?
- Have you made noticeable progress in strength or repetitions over time?
- Are recent sets feeling easier or harder than expected?
- Has training volume or intensity changed recently?
- Have you taken time off from training and are now returning?
You do not need to test failure every session, but you should do it often enough to land in a good range of estimates.
Understanding RIR in relation to MacroFactor Workouts
If you’re using MacroFactor Workouts, the app uses a smart progression algorithm to help make suggestions based on your logged performance.
In MacroFactor Workouts, RIR starts at 0 and goes to 6. A lower RIR, such as 0 to 1, means you were very close to your limit. A higher RIR, such as 4 to 6, means the set felt easier and you had more reps left in reserve.
Let’s say you have a program where you are doing barbell back squats, and you log that you lifted roughly 275lb for 5 reps. The app does not know if that set represents a deload, a moderate working set, or something close to your maximum. However, if you also log that 275lb felt like roughly 2 RIR, the app can estimate that your strength capacity may fall within a higher range – for example, around 305-325lb. It can then adjust your progression accordingly based on the algorithm.
In short, RIR helps the app understand how hard each set actually was, not just how many reps you completed or how much weight you used. This allows recommendations to better reflect your actual effort and fatigue over time.
You can read more about smart progression here and updating RIR targets here.
Takeaways
For any resistance training program, you want to establish a system for estimating your efforts during lifts. There are many methods you can use, but currently one of the most practical and widely used approaches is reps in reserve (RIR).
While it is a system with limitations, it does a good job of helping you estimate effort and stay within an effective range of intensity for progressing in your lifts. And what’s more, you do not need perfect accuracy for RIR to be useful, you just need to be consistent and work on your own estimates.
Lastly, if you’re using MacroFactor Workouts, RIR becomes even more valuable because it helps the system understand how hard your sets actually were. This context allows the app to make better recommendations and adjust your progression based on reported effort, not just the numbers you logged.
Some final tips
- There is often a tendency to underestimate your RIR slightly, so make sure you are safely pushing your limits and occasionally testing where failure actually occurs.
- Warm up properly and continue to assess effort as the set progresses, not just at the beginning, to improve your accuracy.
- Stay conscious of your RIR during training. Avoid being passive or assuming the effort level; instead, test it.
- Periodically taking your last set of an exercise to failure can be a useful way to recalibrate your estimates.
- Working at lower repetitions or closer to failure can sometimes make effort easier to judge than very high-repetition sets, especially when learning the system.
