RIR & RPE Explained

How hard should you train each set? Percentage-based programs don’t account for daily fluctuations in strength and fatigue. RIR and RPE are modern tools for autoregulating your training intensity based on how you actually feel.

What Is RIR?

Reps In Reserve (RIR) is simply how many more reps you could have done before technical failure. It’s a way to describe proximity to failure without actually failing.

• RIR 0: You literally could not do another rep (failure)
• RIR 1: You could have done 1 more rep
• RIR 2: You could have done 2 more reps
• RIR 3: You could have done 3 more reps

What Is RPE?

Rate of Perceived Exertion (RPE) is a 1-10 scale that describes how hard a set felt. For strength training, it’s typically used on a 6-10 scale where:

RIR vs RPE: What’s the Difference?

RIR focuses specifically on reps left. More intuitive for beginners. “I could have done 2 more reps.”

RPE is a broader scale that includes half-values. Preferred by advanced lifters and coaches for precision.

In practice, they’re interchangeable. RPE 8 = RIR 2. Use whichever makes more sense to you.

Why Use RIR/RPE?

Your strength fluctuates daily based on sleep, stress, nutrition, and accumulated fatigue. Fixed percentages can’t account for this.

Example: Your program says “80% × 5 reps.” On a bad day, 80% might be RPE 10 (grinding). On a good day, it’s RPE 7 (easy). By prescribing “5 reps @ RPE 8” instead, you self-adjust the weight to match your daily capacity.

How to Use RIR/RPE in Training

For Hypertrophy (Muscle Growth)

Most sets should be at RIR 1-3 (RPE 7-9). Going to failure on every set isn’t necessary and increases fatigue without proportional gains.

• Compound movements: RIR 2-3 (RPE 7-8)
• Isolation movements: RIR 0-2 (RPE 8-10)

For Strength

Training for maximal strength typically uses RIR 1-2 (RPE 8-9) on main lifts. Going to failure too often compromises technique and recovery.

For Beginners

Start by learning what failure feels like (safely). Most beginners underestimate their true capacity. What they call “RPE 10” is often RPE 7-8.

Common Mistakes

1. Sandbagging: Underestimating capacity and stopping too early
2. Ego lifting: Claiming RPE 7 when it was clearly RPE 10
3. Not tracking: RIR/RPE is useless if you’re not logging it
4. Ignoring trends: If RPE is climbing week over week at the same weight, fatigue is accumulating

Pro tip: Record video of your sets occasionally. Compare what you said the RPE was vs. what the video shows. Most people are off by 1-2 points.

The Sweet Spot

For most training goals, aim for this range:

• Working sets: RPE 7-9 (RIR 1-3)
• Last set of an exercise: RPE 8-9 (RIR 1-2)
• Testing/PR attempts: RPE 9.5-10 (RIR 0-1)