What Are RPE and RIR?
Both RPE and RIR are tools for autoregulation—adjusting your training based on how you feel rather than following fixed percentages. They help you train hard enough to stimulate growth without constantly burying yourself.
Rate of Perceived Exertion (RPE)
RPE uses a 1-10 scale where 10 is absolute maximum effort—you couldn't do another rep if someone paid you. Originally developed for cardio (the Borg scale), it was adapted for resistance training by powerlifter Mike Tuchscherer.
Reps in Reserve (RIR)
RIR is more direct: how many more reps could you have done before failure? If you finished a set and could have done 2 more, that's 2 RIR. Zero RIR means you hit failure.
The RPE-RIR Scale Comparison
| RPE | RIR | Description |
|---|---|---|
| 10 | 0 | Maximum effort, couldn't do another rep |
| 9.5 | 0-1 | Maybe could have done one more, maybe not |
| 9 | 1 | Definitely could have done 1 more rep |
| 8 | 2 | Could have done 2 more reps |
| 7 | 3 | Could have done 3 more reps |
| 6 | 4+ | Light work, significant reps left |
| 5 or below | 5+ | Warm-up territory |
When to Use Each
Use RIR When:
- You're new to autoregulation training
- You want concrete, easy-to-understand targets
- Training isolation movements (easier to gauge)
- Following a program that prescribes specific RIR values
Use RPE When:
- You have experience gauging your effort
- You want more nuanced feedback (half-points like 8.5)
- Training compounds where failure is harder to predict
- Communicating with coaches or training partners
Optimal Intensity for Hypertrophy
Research consistently shows that training within 1-3 reps of failure (RPE 7-9 / 1-3 RIR) produces similar hypertrophy to training to failure—but with less fatigue.
The sweet spot for most working sets:
- Compounds: RPE 7-8 (2-3 RIR) — saves joints and CNS
- Isolations: RPE 8-9 (1-2 RIR) — can push harder safely
- Last set of exercise: RPE 9-10 (0-1 RIR) — if desired
Going to failure on every set isn't necessary and creates excessive fatigue that can limit overall training volume.
How to Get Better at Gauging Intensity
- Start with RIR — After each set, ask "how many more could I have done?" Write it down.
- Occasionally test to failure — On safe exercises (machines, isolations), actually go to failure to calibrate.
- Record your sets — Video RPE 10 looks different than RPE 7. The grind, bar speed, and facial expressions differ.
- Track over time — Compare your RPE estimates to actual performance. You'll get better.
Practical Application
A typical hypertrophy program might prescribe:
- Squat: 3x8 @ RPE 8
- RDL: 3x10 @ 2 RIR
- Leg Press: 3x12 @ RPE 9 (last set to failure)
This means: do weights that leave you with the specified reps in reserve. The actual weight will vary day to day based on sleep, stress, nutrition, and accumulated fatigue—and that's the point.
Frequently Asked Questions
What is the difference between RPE and RIR?
RPE is a 1-10 scale of overall perceived effort. RIR directly counts remaining reps before failure. They're related—RPE 8 equals about 2 RIR—but measure slightly different things.
Is RPE or RIR better?
Neither is universally better. RIR is more concrete and beginner-friendly. RPE allows more nuance. Many lifters use them interchangeably.
What RPE should I train at for muscle growth?
Most hypertrophy work should be at RPE 7-9 (1-3 RIR). This stimulates growth while allowing recovery. Training to failure can be used sparingly.
The Bottom Line
RPE and RIR are two sides of the same coin. Both help you train intelligently by autoregulating based on daily readiness rather than rigid percentages.
Start with RIR if you're new—it's more concrete. Graduate to RPE as your body awareness develops. Either way, aim to spend most of your training at 1-3 reps from failure.
The goal isn't perfect accuracy. It's building the habit of paying attention to how hard you're actually working.