RPE and RIR Explained: Auto-Regulate Your Training

What Is RPE?

Ever finished a set and thought “I could’ve done two more reps”? Congratulations, you already understand RPE. RPE — Rate of Perceived Exertion — is just a formal way of scoring that feeling on a 1-10 scale. It turns your gut instinct into a training tool that automatically adjusts for good days, bad days, and everything in between.

In the context of lifting weights:

RPE 10 = Maximum effort. You could not have done another rep.
RPE 9 = Very hard. You might have had one more rep.
RPE 8 = Hard. You could have done 2 more reps.
RPE 7 = Moderate. You had 3 more reps in the tank.
RPE 6 = Light. Warm-up territory. 4+ reps left.

Most productive training happens between RPE 7 and RPE 9.

What Is RIR?

RIR stands for Reps in Reserve — the estimated number of additional reps you could have completed before reaching muscular failure. It’s the inverse of RPE and, for many lifters, more intuitive to think about.

0 RIR = Failure. No more reps possible.
1 RIR = One rep left in the tank.
2 RIR = Two reps left.
3 RIR = Three reps left.

The RPE-RIR Relationship

RPE and RIR are two sides of the same coin. Here’s how they map to each other:

RPE	RIR	Description
10	0	Maximum effort — absolute failure
9.5	0-1	Could not have done another full rep, but maybe a partial
9	1	One rep left in reserve
8.5	1-2	Definitely had one more, maybe two
8	2	Two reps in reserve
7.5	2-3	Solidly between two and three reps left
7	3	Three reps in reserve — a comfortable working set
6	4	Four reps left — warm-up or speed work
5	5+	Light effort — technique practice

Most hypertrophy training sits between RPE 7 and RPE 9 (1-3 RIR). Most strength training peaks at RPE 8 to RPE 9.5 (0-2 RIR). Going to RPE 10 regularly is generally not recommended outside of competition or planned max attempts — it creates excessive fatigue without proportional benefit.

Why Use RPE Instead of Percentages?

Traditional percentage-based programming tells you to lift a specific percentage of your one-rep max (1RM). For example: “Squat 80% of 1RM for 3 sets of 5.” This works, but it has limitations.

The Problem with Percentages

Your true 1RM fluctuates daily based on:

Sleep quality — a bad night can drop your performance by 5-10%
Nutrition — underfuelled sessions feel harder
Stress — work, relationships, and life all affect the gym
Accumulated fatigue — week 4 of a programme feels harder than week 1
Time of day — most people are stronger in the afternoon than early morning

If your programme says “lift 85% of your 1RM” but today is an off day, 85% might actually feel like 95%. You’ll grind through ugly reps, accumulate excessive fatigue, and increase injury risk.

The RPE Advantage

RPE-based programming adapts to your daily state. “Squat at RPE 8 for 3 sets of 5” means you use whatever weight allows you to leave 2 reps in the tank — regardless of whether that’s 82% or 88% of your theoretical max on any given day.

On great days, you’ll naturally lift heavier. On bad days, you’ll back off appropriately. The training effect is the same because the relative effort is the same.

How to Use RPE in Your Programming

For Hypertrophy (Muscle Growth)

Most sets should land between RPE 7 and RPE 9. Training to failure (RPE 10) on every set is not necessary for growth and creates disproportionate fatigue.

A solid approach:

Compound lifts (squat, bench, deadlift): RPE 7-8
Accessory lifts (curls, lateral raises, leg curls): RPE 8-9
Final set of an exercise: RPE 9 (push a little harder)

For Strength

Top sets should be heavier and closer to failure, but back-off sets should be controlled:

Top set: RPE 8.5-9.5
Back-off sets: RPE 7-8

Practical Example

Here’s how RPE might guide a bench press session:

Warm-up: Bar x 10, 40kg x 8, 60kg x 5 (all RPE 4-5)
Working Set 1: 90kg x 5 — felt like RPE 7.5. Good.
Working Set 2: 92.5kg x 5 — RPE 8. Right on target.
Working Set 3: 92.5kg x 5 — RPE 8.5. Fatigue building, but still in range.
Working Set 4: 92.5kg x 4 — RPE 9. Couldn’t get rep 5. Stop here.

Without RPE, you might have blindly pushed for a 5th rep on that last set and either failed the rep or ground out something ugly. With RPE, you self-regulate and keep the quality high.

How to Get Better at Gauging RPE

RPE is a skill. Beginners often underestimate how many reps they have left (calling RPE 8 when it’s really RPE 6). Here’s how to calibrate:

1. Occasionally Test to Failure

On isolation exercises (where it’s safe), take your last set to true failure once every few weeks. This recalibrates your internal gauge. If you thought you had 2 reps left and you actually got 4, you know your RPE sense needs adjustment.

2. Use Video

Film your sets and review bar speed. The last 2-3 reps before failure typically show a noticeable slowdown. Over time, you’ll learn to feel that deceleration in real time.

3. Track RPE Alongside Weight and Reps

After every set, write down the weight, reps, and your RPE estimate. Over weeks, patterns emerge. You’ll learn that “95kg for 5 on bench at RPE 8” is your consistent threshold, which makes it easier to judge in future sessions.

4. Be Honest

RPE only works if you’re honest with yourself. Nobody is watching. Nobody cares. If the set was easy, call it easy. If it was a grinder, call it a grinder.

Common Mistakes

Treating RPE 10 as the Default

Training to failure every set is not the goal. RPE 10 has its place — in max-out tests, competition, or occasional intensity techniques — but most training should stop 1-3 reps short of failure.

Confusing “Hard” with “Heavy”

A set of 15 reps at RPE 9 doesn’t need to be heavy. RPE measures effort relative to capacity, not absolute load. Light-weight, high-rep sets taken close to failure are high RPE too.

Ignoring RPE on Easy Days

RPE is most valuable when things don’t go to plan. If the programme says RPE 8 and today’s RPE 8 weight is 10kg less than last week, that’s fine. Trust the system. Forcing last week’s numbers when your body isn’t ready defeats the purpose.

Not Logging It

RPE without a training log is just a feeling. Write it down so you can spot trends and make informed decisions about progression.

Key Takeaways

RPE (1-10) measures how hard a set felt; RIR measures how many reps you had left
Most training should sit between RPE 7 and RPE 9 (1-3 reps in reserve)
RPE adapts to your daily readiness — it’s smarter than rigid percentages
Getting good at RPE takes practice: film sets, occasionally go to failure, and always log your numbers
Be honest with your ratings — the whole system depends on it