RPE and RIR Explained: How Hard Should Your Sets Be?

Writing "3 sets of 8" says nothing about how hard those sets were. Eight reps with a weight you could lift twenty times is a warm-up; eight reps that leave nothing in the tank is a maximal effort. RPE and RIR describe that difference with a number.

The Two Scales

RIR (reps in reserve) is how many more reps you could have done with good form. Stop with two left in the tank and that set is RIR 2.

RPE (rate of perceived exertion) in lifting is usually a 1–10 scale linked to RIR: RPE 10 means no reps left, RPE 9 means one left, RPE 8 means two left, and so on. They are two ways of saying the same thing.

How Hard Is Hard Enough?

For building muscle and strength, most working sets land well between RIR 1 and RIR 3 — hard, but not to failure. Sets that are much easier than that do less to drive progress. Going to absolute failure on every set adds fatigue faster than it adds results, especially on big lifts like squats and deadlifts. For more on that trade-off, see training to failure.

Beginners Underestimate

Most new lifters stop sets far earlier than they think. A set that feels like RIR 1 is often RIR 4 or 5. Two ways to calibrate:

• On a safe exercise, like a machine or dumbbell curl, occasionally do a set to true failure. Compare what you predicted with what happened.
• Record your predicted RIR in your notes and check it against the reps you manage the next time you use the same weight.

Using RPE to Auto-Regulate

RPE lets your training flex with your day. If the plan says 5 reps at RPE 8 and you slept badly, the weight that hits RPE 8 might be a little lighter. On a great day, it might be heavier. You still get the right training effect without forcing a number that does not fit the day.

A Simple Way to Start

Add one number to each working set in your notes: how many reps you think you had left. In a few weeks you will have a feel for effort that is far more useful than the weight alone.