RIR vs. RPE: What's the Difference — and Which Should You Use?
RPE and RIR are two systems for measuring training intensity — without percentages, without a 1RM test. Both describe how close you train to muscular failure. The difference is smaller than most people think.
RPE Explained
RPE stands for Rate of Perceived Exertion — your subjective sense of effort. Originally developed by Gunnar Borg as a 6-20 scale for endurance, it was adapted for strength training into a 1-10 scale.
| RPE | Meaning |
|---|---|
| 10 | Muscular failure — no more reps possible |
| 9 | Could have done 1 more rep |
| 8 | Could have done 2 more reps |
| 7 | Could have done 3 more reps |
| 6 | 4+ more reps — light warm-up feeling |
RPE 8 means: “I could have done 2 more clean reps, but I stopped.”
RIR Explained
RIR stands for Reps in Reserve — the number of additional reps you could have performed.
| RIR | Meaning |
|---|---|
| 0 | Muscular failure — no more reps possible |
| 1 | 1 more rep possible |
| 2 | 2 more reps possible |
| 3 | 3 more reps possible |
| 4+ | Light effort |
RIR 2 means: “I could have done 2 more reps.”
RPE vs. RIR: The Mapping Table
The conversion is simple:
| RPE | RIR | Interpretation |
|---|---|---|
| 10 | 0 | Muscular failure |
| 9.5 | 0-1 | Maybe 1 more rep |
| 9 | 1 | 1 rep in reserve |
| 8.5 | 1-2 | 1-2 reps in reserve |
| 8 | 2 | 2 reps in reserve |
| 7.5 | 2-3 | 2-3 reps in reserve |
| 7 | 3 | 3 reps in reserve |
Formula: RPE = 10 − RIR
That’s it. RPE 8 = RIR 2. RPE 9 = RIR 1. Two sides of the same coin.
When RPE Makes More Sense
RPE has one advantage over RIR: The modified RPE scale allows half-steps (7.5, 8.5, 9.5). This gives you more granularity in your assessment.
RPE is also the more established system in coaching literature. When your program says “3×8 @ RPE 8,” everyone knows what that means.
Use RPE when:
- Your program prescribes RPE values
- You want to use half-steps (8.5 instead of “somewhere between RIR 1 and 2”)
- You work with a coach who uses RPE
When RIR Makes More Sense
RIR is more concrete and intuitive for many lifters. “2 reps in reserve” is easier to understand than “RPE 8” — especially for beginners who aren’t familiar with the Borg concept.
Use RIR when:
- You find “how many more reps could I have done?” more intuitive
- You’re coaching beginners (the question “How many reps did you have left?” is immediately understandable)
- You want to count effective sets (RIR 0-3 = effective set)
In Practice: Most Programs Use Both
Here’s the truth: in practice, most programs and coaches use RPE and RIR interchangeably. “3×8 @ RPE 8” and “3×8 @ RIR 2” are identical instructions.
The choice between RPE and RIR isn’t a scientific decision — it’s a preference. Both systems:
- Autoregulate intensity (you adjust weight based on how you feel that day)
- Avoid fixed percentage training (which responds poorly to daily fluctuations)
- Require practice and calibration (beginners often overestimate their RIR)
The key point: Regardless of whether you use RPE or RIR — be honest with yourself. A set you log as “RPE 8” when you were actually at your limit distorts your tracking.
→ RPE vs. Percentages: Which system is better?
Logging RPE and RIR in Your Training
In the Workout Screen, you can log RPE or RIR for each set. Which system you use is up to you — the plans in hitPR drive progression through built-in rules (AMRAP, double progression, scheme changes), not through RPE.
The benefit of logging: Over time, you build an honest picture of how the same weights feel. That helps you judge whether you’re well recovered or whether life is getting in the way.
Bottom Line
RPE and RIR are the same concept in different packaging. RPE 8 = RIR 2. Choose whichever system feels more intuitive. What matters more than the scale is the honesty of your assessment — and that comes with experience.
Further reading:
Sources
- Zourdos MC et al. (2016). Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve. Journal of Strength and Conditioning Research, 30(1):267-275.
- Helms ER et al. (2018). RPE and Velocity Relationships for the Back Squat, Bench Press, and Deadlift in Powerlifters. Journal of Strength and Conditioning Research, 32(2):292-297.
