Reps in reserve (RIR) is the number of clean reps you could still have done when you racked the bar. Finish a set of 5 knowing you had two more in you, and that set was 5 reps at 2 RIR. That's the whole definition.
The gym-bro version of hard training says every set should end in a grind, a spotter and a face the color of a stop sign. After 40, that approach runs into a wall fast. Recovery is the limiting factor now, not effort. RIR is how you keep training hard while leaving the part of the set that costs the most and builds the least in the tank.
What reps in reserve actually measures
RIR is a guess about the future. You're estimating how many more reps you could have finished with good form before the bar stopped moving. It isn't about how you feel, how sweaty you are, or how loud the music is.
That makes it different from the old 1-to-10 "how hard was that" scale. The version lifters use today was built specifically around reps left in the tank, and it's become the standard way to rate a set in strength training [1][2].
A few rules keep the number honest:
- Count clean reps only. If the next rep would have been a half squat or a bench with your butt off the pad, it doesn't count.
- Rate it right after the set. Wait five minutes and the story always gets better.
- Rate the set, not the day. A bad night of sleep doesn't change the definition. It just changes where the number lands.
RIR vs RPE: same idea, different direction
You'll see RPE (rating of perceived exertion) on most programs. In lifting, RPE and RIR are two ways of writing the same thing. RPE 10 means nothing left. Every point below 10 is one more rep in reserve.
| RPE | RIR | What it feels like |
|---|---|---|
| 10 | 0 | Nothing left. Another rep would fail. |
| 9 | 1 | One more rep, and it would be ugly. |
| 8 | 2 | Two more clean reps. Hard but controlled. |
| 7 | 3 | Bar speed still good. Solid working set. |
| 6 | 4 | Warm-up to moderate. Practice weight. |
If a program says "3x5 @ RPE 8," it's asking for sets of 5 where you finish with about two reps left. Same instruction as "3x5 at 2 RIR." Use whichever one sticks in your head.
Why RIR matters more after 40
Three things change as you get older, and RIR handles all three.
Your readiness swings more. At 25, Tuesday's session looked a lot like Thursday's. Past 40, sleep, work stress, and a cranky joint can move your strength a few percent in either direction from one session to the next. A fixed percentage program can't see any of that. A set taken to 2 RIR adjusts on its own: on a good day the weight moves and you add load, on a bad day you hit the same effort with less on the bar. That's the core idea behind autoregulation.
The last reps are the expensive ones. The final grinding reps of a set pile on the most fatigue for the least extra benefit. Research on proximity to failure points the same way: for strength, stopping a couple of reps short costs very little, while muscle growth benefits more from getting closer to failure [3]. For most lifters over 40 chasing strength that lasts, that's a clear trade. Leave the grinders for when they matter.
Tendons and joints adapt slower than muscle. Your muscles can handle more than your connective tissue can for a while. Staying at 1 to 3 RIR on most work keeps tissue loading steady without the bad-rep spikes that turn a sore elbow into six weeks off. This is the same thinking behind submaximal training.
How to get good at rating RIR
Here's the honest part: most people are bad at this at first. Studies on predicting reps to failure show lifters tend to guess wrong when the set is far from failure, and get more accurate as they get closer to it [4]. That's fine. It's a skill, and skills improve with reps.
A simple way to calibrate over the next two weeks:
- Pick one main lift and one accessory. Say squat and dumbbell row.
- On the last set, call your RIR out loud, then keep going to a safe failure. On the squat, that means safety pins set or a real spotter. On the row, just keep going.
- Compare. If you called 2 RIR and got 4 more, you're underrating yourself. Most people do.
- Repeat for 4 to 6 sessions. Your calls will tighten up fast.
You don't need to test to failure forever. Once your guesses land within a rep, stop. Hard sets to true failure on heavy barbell lifts are the exact thing RIR is supposed to save you from.
RIR targets that work after 40
| Goal | Typical RIR | Where it fits |
|---|---|---|
| Technique and speed work | 4 to 5 | Warm-ups, deload weeks, practice |
| Most strength work | 2 to 3 | Main barbell lifts, week in and week out |
| Heavy top sets | 1 to 2 | One set per session, not every set |
| Muscle building accessories | 0 to 2 | Machines, dumbbells, cables, where failure is safe |
| Max testing | 0 | Rarely. Most of us don't need it at all. |
The pattern: the heavier and more technical the lift, the more reps you leave. A leg extension to failure costs you almost nothing. A deadlift to failure can cost you a week.
Using RIR to estimate your max without testing it
This is where RIR earns its keep. Any hard set you log with an honest RIR is enough to estimate your one rep max. No max day, no spotter, no wrecked week.
The idea is simple: add the reps you left back onto the reps you did, then run a standard estimate. A set of 5 at 2 RIR is treated like a 7-rep max. From there, the Epley formula (weight x (1 + reps / 30)) gets you a working number. If you want the math explained, see how to calculate your 1RM.
If you'd rather skip the math, the 1RM calculator at Center Mass Strength takes weight, reps and RPE, adds the reserve back for you, and builds a full percentage chart and rep max table from the result. Log a top set, plug it in, and you have training weights for the next block.
A couple of guardrails:
- Use your first hard set, not set four after the fatigue has piled up.
- Hold your normal standards. A high squat or a bounced bench inflates the estimate and every weight built on it.
- Recheck every few weeks. If your top sets start moving faster than the RIR you're calling, your max has gone up. Update it. That's progressive overload done right.
Common RIR mistakes
Sandbagging. Calling 3 RIR on sets that really had 5 or 6 left. The work feels productive and isn't. The calibration drill above fixes this.
Letting ego pick the number. Calling 2 RIR on a set that was really a grinder, because 2 sounds better. The bar speed doesn't lie. If the last rep slowed to a crawl, it was 0 or 1.
Chasing a target on a bad day. The plan says 5 @ RPE 8 and the warm-ups feel like concrete. The right move is to take weight off until 5 reps lands at 2 RIR, not to force the planned load. That's the whole point. If bad days start stacking up, read up on overreaching vs overtraining before you push through, and don't be afraid of a planned deload.
Using RIR where failure is dangerous and pretending you're not. Ratings on heavy squats and deadlifts should stay conservative. Save 0 RIR for exercises where failing is boring.
Start this week
You don't need a new program to use this. On your next session, add one number to your log for every working set: the RIR you finished at. Two weeks of that and you'll know more about how you actually train than most lifters learn in a year.
Useful sources and further reading
- Zourdos MC, et al. Novel resistance training-specific rating of perceived exertion scale measuring repetitions in reserve. J Strength Cond Res. 2016;30(1):267-275. PubMed
- Helms ER, Cronin J, Storey A, Zourdos MC. Application of the repetitions in reserve-based rating of perceived exertion scale for resistance training. Strength Cond J. 2016;38(4):42-49. PubMed
- Robinson ZP, 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. PubMed
- Halperin I, et al. Accuracy in predicting repetitions to task failure in resistance exercise: a scoping review and exploratory meta-analysis. Sports Med. 2022. PubMed
FAQ
What does reps in reserve mean?
Reps in reserve (RIR) is the number of clean reps you could still have done when you ended a set. A set of 8 with two reps left is 8 reps at 2 RIR.
What is the difference between RIR and RPE?
In lifting they describe the same thing from opposite ends. RPE 10 equals 0 RIR, RPE 9 equals 1 RIR, RPE 8 equals 2 RIR. Most programs use RPE, and you can convert in your head by subtracting from 10.
How many reps in reserve should I leave after 40?
For most strength work, 2 to 3 RIR on your main lifts. Take one heavier top set at 1 to 2 RIR if the day is good, and save sets to failure for accessories where failing is safe.
Is training to failure bad after 40?
Not on its own, but it's expensive. Going all the way to failure on heavy barbell lifts piles on fatigue with little extra strength payoff. Keep failure for machine and dumbbell work, and stay a couple of reps shy on squats, benches and deadlifts.
Can I use RIR to estimate my one rep max?
Yes. Add your reps in reserve to the reps you did, then use a formula like Epley. A set of 5 at 2 RIR is treated like a 7-rep max. A 1RM calculator that accepts RPE will do the conversion for you.
