Reps in reserve, or RIR, is your estimate of how many more repetitions you could complete before reaching the exercise's defined stopping point. A set at 2 RIR ends when you think you could perform two more reps with the same technique and range. It does not mean completing two additional reps after you have already decided to stop.
For a straightforward training example, use an 8–12-rep range with about 2 RIR. Choose a load that lets you reach the range without exhausting every possible repetition, record the reps you completed, and adjust the next set if the load clearly misses the intended effort. This is a practical example for generally healthy adults, not a universal effort target.
Read the scale before choosing a weight
| RIR | What you estimate at the end of the set | What it does not mean |
|---|---|---|
| 4 or more | Several more controlled reps were available. | The set was pointless. |
| 3 | About three more reps were available. | Exactly three extra reps have been measured. |
| 2 | About two more reps were available. | You must perform two more now. |
| 1 | About one more controlled rep was available. | You should attempt a rep you cannot control. |
| 0 | No further complete rep was available under the same standard. | You need to become trapped under a bar to prove it. |
The standard matters. If you could do two more reps only by bouncing the weight, shortening the movement or using assistance, those are not two repetitions in reserve under the original standard.
Before estimating effort on a new movement, review its instructions. Beacon's chest-supported row, leg press and lateral raise references include demonstrations to help identify the exercise being discussed. A demonstration introduces the movement; it cannot assess your individual technique or symptoms.
RIR is different from feeling tired
A set can burn, leave you breathing hard or feel mentally unpleasant while several reps remain. Those sensations are real, but they do not tell you the exact number of further repetitions you could perform.
It also helps to separate two stopping points:
- Technical limit: another repetition would require a meaningful change in the technique or range you intended to use.
- Momentary muscular failure: you attempt another repetition but cannot complete it despite trying.
These are related, but they are not interchangeable descriptions. For everyday practice, specify the technique you intend to preserve and stop when you can no longer maintain it. Do not force a failed rep under an unprotected bar to obtain an RIR rating.
Pain, dizziness or loss of control are reasons to stop and assess what is happening. They are not proof you reached an effective training effort.
A worked example: three sets of rows
Imagine a familiar chest-supported row prescribed for three sets of 8–12 reps at about 2 RIR. After lighter preparation sets, you use the same bench setup and rest about two minutes between working sets. The following is an illustrative decision sequence, not a required load or rest interval.
| Set | Result | Your estimate | Practical response |
|---|---|---|---|
| 1 | 10 controlled reps | About 2 left | The load fits the example. Rest and repeat it. |
| 2 | 9 controlled reps | About 2 left | Fewer reps can still meet the same effort target. |
| 3 | 8 controlled reps | About 2 left | Finish the prescribed work; record the actual result. |
You do not have to force all three sets to 10. Doing so could turn the last set into an all-out effort that differs from the prescription.
Now consider two ways the first set could miss:
- You reach 12 and believe six or more controlled reps remain. The load is probably too light for this example's combined rep and effort targets. At the next set or session, consider a small increase rather than adding unlimited extra reps. Account for the equipment increments available.
- You reach eight only by changing your technique, with no controlled rep left. The load is too demanding for the example. Reduce it, recover between sets, and aim for controlled repetitions within the range.
If you are learning the exercise and cannot judge either case confidently, use an easier load and focus on repeating a consistent movement. An experienced coach can help assess execution without requiring you to fail.
How close to failure should you train?
The answer depends on the program, exercise, experience and goal. For the example in this guide, about two reps left provides a clear effort target without asking you to attempt a failed repetition on every set. Learning a movement may call for more reserve; a specific program may deliberately prescribe something different.
There is direct evidence that training to failure is not necessary in every productive set. In an eight-week trial by Refalo and colleagues, 18 trained adults performed leg press and leg extension work with each leg assigned to failure or perceived 1–2 RIR. Quadriceps growth was similar between conditions, while the failure condition produced greater losses in repetition performance and lifting velocity. That result concerns particular lower-body exercises, people and training conditions; it does not prove every muscle or routine responds identically.
The ACSM's 2026 resistance-training update likewise does not make failure training a requirement for the average healthy adult. There is little reason to turn every ordinary session into a test of the last possible rep.
How accurate is your estimate?
RIR is a judgment, not a sensor reading. Its usefulness depends on the task you are judging and how consistently you define a repetition.
Research has tested that judgment by asking trained participants to indicate their predicted reserve during a set, then continuing to failure to establish how many reps remained. A bench press study of 1- and 3-RIR predictions used that approach in 24 trained men and women at 75% of their maximum. The protocol is much more specific than asking whether everyone can estimate effort accurately on any exercise.
You do not need to reproduce a laboratory failure test to start using the idea. Instead:
- Use familiar exercises and consistent setup, range and rest.
- Make your estimate near the end of the set rather than assuming the first few reps reveal the eventual effort.
- Record a rough estimate such as “about 2–3 left” if that is more honest than a precise number.
- Compare sessions and seek coaching if you repeatedly misjudge obvious easy or all-out sets.
The aim is a useful shared description of effort. Giving every set a confident number does not make it accurate.
RIR and RPE: check which scale the program uses
Some lifting programs use an RIR-based rating of perceived exertion, or RPE. Near the hard end of that particular scale, RPE 10 corresponds to 0 RIR, RPE 9 to about 1 RIR, and RPE 8 to about 2 RIR.
That mapping is a naming convention for a lifting scale, not a rule for every RPE system. A whole-workout exertion rating or a cardio effort scale may ask a different question. Check the program's definition rather than translating every “8 out of 10” into two remaining repetitions.
Use effort alongside reps, load and rest
Suppose you previously completed 12 reps with about two left. Next time you complete 12 only by reaching your technical limit. The rep count is identical, but the task cost you more effort. That is useful context before deciding to increase the load.
For a simple double-progression approach, hold the load until all prescribed sets reach the top of the rep range at the intended effort and technique. Then try a suitable small increase. If performance drops, check rest, exercise order and setup before assuming you need more weekly sets.
If an exercise is unavailable, a suitable alternative changes the baseline. For example, a familiar machine row can replace a supported dumbbell row when equipment is limited, but its stack number is not the same load. Review the replacement's instructions and choose its load from how you perform that movement.
Apply it to a program in Beacon
For iPhone users who want strength training together with nutrition, habits and health context, Beacon is our top recommendation for following and logging the broader routine. It is not a claim that the app can measure your remaining reps or correct your technique.
Start with the beginner full-body program or inspect the upper/lower program. Choose appropriate exercise loads, log the repetitions you actually complete, and use an effort target you understand. Get Beacon for iPhone if you want those workouts alongside your other routines; keep your own written effort notes wherever you normally record training context.