Reps in reserve measures how close a set was to failure. Learn how to rate RIR accurately, what range to train in, and how it drives smarter weight increases.
Reps in reserve (RIR) is the number of clean reps you could still have done when you ended a set. 0 RIR means you could not do another rep, 2 RIR means you stopped two short. Most working sets should finish at 1 to 3 RIR, which is hard enough to drive progress without the extra fatigue of constant failure. Rating every set lets you decide objectively when to add reps or weight.
Two lifters both write "bench 185 × 8" in their logs. One finished the set with three more reps in the tank. The other barely got the eighth rep up. Next session, they should do different things, but their logs look identical.
Reps in reserve fixes that. It is a simple number that tells you how hard a set really was, and once you start recording it, your training decisions get far less guesswork.
Reps in reserve (RIR) is how many more reps you could have performed with good technique before reaching failure. If you stop a set of squats and honestly believe you had two more clean reps, that set was 2 RIR.
| RIR | What it feels like |
|---|---|
| 4 or more | Comfortable. Warm-up territory |
| 3 | Challenging but controlled |
| 2 | Hard. Bar speed slowing |
| 1 | Very hard. One more rep, maybe |
| 0 | Nothing left. The next rep would fail |
"Failure" here means technical failure: the point where you could not complete another rep with the form you would accept. It does not mean the point where your lower back takes over.
RPE stands for rating of perceived exertion. The version most lifters use today is tied directly to RIR: RPE 10 means 0 RIR, RPE 9 means 1 RIR, RPE 8 means 2 RIR, and so on. A 2016 study by Zourdos and colleagues introduced this RIR-based RPE scale for resistance training and found it tracked well with bar speed. Helms and colleagues published a practical guide the same year on how to use it to regulate training loads.
RIR is often easier to think about because it is a concrete count. "Could I have done two more?" is a simpler question than "Was that an 8?"
Reps and weight tell you what you did. RIR tells you how much it cost. That changes the decisions you make:
For most lifters, most of the time: 1 to 3 reps in reserve on working sets.
A 2023 meta-analysis by Refalo and colleagues looked at proximity to failure and muscle growth. Training to failure did not produce meaningfully more hypertrophy than stopping short of it. That matters, because sets taken to failure produce more fatigue and take longer to recover from, which can eat into the quality of your later sets and sessions.
That does not mean easy training works. Sets ended with 5 or more reps in reserve are unlikely to give you the same stimulus. The sweet spot is genuinely hard sets that stop a little before the wall.
Somewhat. A practical approach:
Most people underestimate how many reps they have left, particularly on higher-rep sets and early in their training. In the Zourdos study, experienced lifters rated their efforts more accurately than novices did. Accuracy is a skill you build.
Ways to sharpen it:
Use words instead. A five-point scale works well:
| Rating | Approximate RIR |
|---|---|
| Very easy | 4 or more |
| Easy | 3 |
| Moderate | 2 |
| Hard | 1 |
| Max effort | 0 |
Most people find "that was hard" more natural than "that was 1 RIR," and the information is nearly the same.
RIR turns progression from a guess into a rule. Here is an example with a lifter doing barbell rows in a 6 to 10 rep range:
| Session | Weight | Reps | RIR on last set | Next step |
|---|---|---|---|---|
| 1 | 155 lb | 8, 8, 7 | 1 | Add a rep |
| 2 | 155 lb | 9, 9, 8 | 2 | Add a rep |
| 3 | 155 lb | 10, 10, 10 | 2 | Top of range with reps left, add weight |
| 4 | 160 lb | 8, 7, 7 | 1 | Build reps again |
If session 3 had been 10, 10, 10 at 0 RIR, the smarter call would be to repeat 155 lb and make the sets look easier before jumping.
Alexandros is an iPhone app that works like a personal weightlifting coach you talk to in a chat. Every set you log gets an effort rating on the same five-point scale shown above, from Very easy to Max effort, or you can give reps in reserve directly. Effort maps to RIR the same way: Very easy is about 4 or more, Easy about 3, Moderate about 2, Hard about 1, and Max effort is 0.
You can log by describing a session in plain English, such as "leg press, 4 sets of 12 at 300, felt easy," and it turns that into structured sets with a workout card you can tap to fix any line. Those effort ratings then drive the recommendation for next time. Reaching the top of your rep range with at least one rep in reserve means a weight increase. Reps within the range mean adding one rep, or two if it felt very easy. A ground-out set below the range means backing off about 8 percent. Because every number it gives you comes from your own log, the recommendation reflects how the set actually felt, not just what you lifted.
Less accurate at first, which is normal. Beginners often underestimate how much they have left. It still helps, and accuracy improves within a few weeks of rating honestly. Occasional tests to failure on safe exercises speed this up.
Not necessarily. It is common for the first set to be at 2 to 3 RIR and the last set to drift to 1 as fatigue builds at the same weight. Recording that drift is useful, since it shows how hard the whole exercise was.
Yes, in practice. 0 RIR means you could not have completed another rep with acceptable form. Occasional sets at 0 RIR are fine, especially on isolation lifts, but they should not be the default on heavy compounds.
Warm-ups should be well above 4 RIR. Their job is to prepare you, not to tire you. Only rate and progress your working sets.
