RPE and Reps in Reserve Explained for Beginners
By Answer Fitness editorial ·
Reps in reserve (RIR) means how many more repetitions you could have done with the same form. A resistance-training RPE scale is the same idea written as a number: an 8 usually means about two reps left, a 9 means about one, and a 10 means you could not have done another. Beginners can use the plain version — stop with one to three reps left — without treating the number as a lab measurement.
The words, once
A repetition is one full lift. A set is a group of them. Failure means you cannot complete another rep with the form you started with. RIR counts the reps you did not do. RPE here is the repetitions-in-reserve scale described by Zourdos and colleagues in 2016, not the older 6–20 scale used for cycling and running.
| RPE on that scale | Reps left | In plain language |
|---|---|---|
| 10 | 0 | No more reps with this form |
| 9 | about 1 | One more was there |
| 8 | about 2 | Two more were there |
| 7 | about 3 | Three more were there |
You do not need to hit 10 to make a set “count.” The 2-day beginner plan asks you to leave 1–3 reps in reserve on purpose.
Why beginners should stay a little shy of failure
Zourdos’s group also found that people are worse at calling reps in reserve when they are far from failure, and when the set has a lot of reps. A beginner guessing “I had five left” is often wrong. Stopping around 1–3 reps left is easier to feel: the last rep slows down, but it still matches the first. If you are not sure, leave the extra rep. Adding load too soon is covered in how to progress your lifts.
This is not a medical test, and it does not replace a clinician’s limit if you are injured or have been told not to strain.
How to use it in a normal session
- Pick a weight you think fits 8–10 reps.
- Stop at 8–10 if the bar speed is still under control and you believe one to three reps remain.
- Write the load, the reps, and a simple note: “2 left” or “RPE 8.”
- If you hit the top of the range with more than three left, add a little weight next time, on the order of the 2–10% step in the ACSM 2009 progression stand.
- If you miss the bottom of the range or form breaks, the weight is too heavy. Rest longer before you decide — see how long to rest between sets.
What not to do with the number
Do not turn every warmup set into a 10. Do not copy someone else’s RPE. Their 8 is not your 8. And do not add sets because a set felt like a 6. Either the weight was light or you are still learning the lift. Log it and move on.
Sources
- Zourdos MC, Klemp A, Dolan C, et al. Novel resistance training-specific RPE scale measuring repetitions in reserve. J Strength Cond Res. 2016.
- Zourdos MC, Goldsmith JA, Helms ER, et al. Proximity to failure and repetitions performed influence RIR accuracy. J Strength Cond Res. 2021.
- American College of Sports Medicine. Progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2009.
Published October 2026. Not medical advice. Cover photos are editorial illustrations, not a test of a specific gym.
