RPE and RIR explained: the 1–10 effort scale for lifting and how to rate a set honestly

RPE and RIR describe the same thing: how close a set came to the point where you could not do another good rep.

• RIR (reps in reserve) counts what was left. Two reps in reserve means you stopped two short of failure.
• RPE (rating of perceived exertion) scores how hard it was on a 1–10 scale, where 10 is nothing left.

In the usual working range, RPE = 10 − RIR. The rest is detail, and the detail is mostly about the ends of the scale.

What does each RPE number mean?

This is the resistance-training scale published by Zourdos and colleagues in 2016. When a program today writes RPE 8 next to a set, this is usually the scale it means.

Two rows break the simple subtraction. RPE 9.5 exists because a heavy single or double can leave you with no more reps but a sense that 2.5 kg more would still have gone up. And everything from RPE 6 down is deliberately vague, because nobody can tell the difference between five and six reps left with any confidence.

Where did the lifting version of RPE come from?

Perceived-exertion scales are older than strength training apps by decades, but the generic ones ask how hard the effort felt, which is a poor fit for a set of squats. Your legs and lungs can feel terrible on a set of 20 that still had reps left in it.

Zourdos and colleagues tied the number to something you can at least try to count. In their study, 29 people (15 experienced squatters and 14 novices) worked up to a one-rep max, then did singles at 60, 75 and 90 percent of it and a set of 8 at 70 percent, rating each with the new scale while bar speed was measured. Ratings and bar speed moved strongly in opposite directions in both groups: as sets got slower, ratings went up. Experienced squatters also rated their true max higher than novices did, which is a hint that the top of the scale takes practice.

A companion paper by Helms and colleagues in 2016 laid out how to use the scale in training, and a 2017 study of 15 powerlifters found very strong relationships between RPE and percentage of max on the squat, bench and deadlift. Even at a true one-rep max, those lifters averaged 9.6 to 9.7 rather than a flat 10.

How accurate are lifters at judging reps in reserve?

Within about a rep, on average, with plenty of individual variation. The best summary is Halperin and colleagues’ 2022 meta-analysis in Sports Medicine, which pooled 12 studies with 414 participants:

• People underpredicted the reps they had left by about 0.95 reps. In other words, they tended to stop a little further from failure than they thought.
• Predictions got more accurate closer to failure. A guess made on the last rep beats one made on the third.
• Sets of 12 reps or fewer were judged far more accurately than longer sets.
• Later sets were slightly more accurate than early ones.
• Training status didn’t seem to matter much. Experience helps you feel at home under a bar, but it doesn’t automatically make the counting accurate.

The variation between studies was large, so treat “about one rep” as a rough figure. The practical reading is that RPE 7 is a fuzzy number and RPE 9 is a fairly sharp one.

How do you rate a set honestly?

These are the rules I use, built around what the research above says goes wrong.

1. Rate the last rep, straight after the set. Not the set as a whole, and not after the rest period, when the memory has already softened.
2. Ask the RIR question, then convert. With the same technique, how many more could I have done? Answer that, subtract from 10, and you have the RPE.
3. Count only good reps. A rep that would have needed a different bar path or a bounce is not in reserve.
4. Use half points only from about 7.5 up. Lower down the scale, the extra precision is imaginary.
5. Calibrate now and then. On a safe exercise, such as a machine or a lift set up with safety arms, predict your reps in reserve on the last set, then keep going to failure and compare. Do it on a few lifts and you learn which direction your own error runs.
6. Expect the same load to rate differently on different days. A short night is the classic cause, and it is the reason the original GymLogger X post told lifters to hold their weights the week the clocks change. A higher RPE on a bad day is useful information about recovery.

One more: don’t rate warm-ups. A warm-up rated RPE 4 tells you nothing you need.

What is autoregulation, and does it work?

Autoregulation means letting the day’s rating set the load instead of a fixed number. A typical version: work up to a top set of 3 at RPE 8, then take a planned amount off that weight for the back-off sets. On a good day the RPE 8 triple is heavier than last week; on a bad one it is lighter, and the plan still holds.

The best controlled comparison I know is Helms and colleagues’ 2018 study. Twenty-one trained men ran the same eight-week, three-days-a-week squat and bench program. One group set loads from percentages of a pre-tested max; the other chose loads to land in target RPE ranges. Both gained strength and muscle thickness. The difference between groups wasn’t statistically significant, and the authors’ probability analysis gave the RPE group a likely small strength advantage. It is one study with 21 people, so the honest summary is that both methods work and RPE loading is at least as good.

The decision rules that sit on top of RPE (when to add load, when a falling top set means you need a lighter week) are in the progression-model table of the program-choosing post. And the same idea runs through estimating your one-rep max: an estimate from a set at RPE 7 reads low, because the formula assumes you went close to failure.

Should you log RPE or RIR?

They carry the same information, so pick the one you will actually record. RIR is easier to start with because it is a count. RPE is handy once you lift heavy singles and doubles, where 9.5 says something RIR can’t. If a program is written in one and you think in the other, convert with 10 − x and move on.

What matters more is consistency. A rating you give every hard set, the same way, builds a record of what a given RPE costs you in kilos. A rating you remember to give once a fortnight is just a mood.

How GymLogger X uses reps in reserve

In GymLogger X, RIR is part of the prescription. When the Smart Program Creator builds a program, each exercise gets sets, a rep range and a reps-in-reserve target, and the program preview shows it alongside them, for example 3 × 8–12 at RIR 2. The targets follow a few fixed rules:

• The starting point depends on the goal. Compound lifts in a hypertrophy program start at 8–12 reps with 2 in reserve; a strength program starts them at 3–6 reps with 1 in reserve; general fitness at 10–15 reps with 3.
• Lifters aged 40 and over get one extra rep in reserve, and 55 and over get two.
• If you tell it about an injury, movements that load that area get two or four extra reps in reserve, depending on the phase you are in.
• In a linear cycle, the target tightens by up to two reps across the weeks before the deload.
• Deload weeks cut the sets roughly in half and raise the reps-in-reserve target, by three in most program styles.

If you import a program from a spreadsheet, the importer reads an RIR column, or an RPE column converted as 10 − RPE.

What GymLogger X doesn’t do is ask you to rate each set. A logged set is the weight and the reps, entered on the iPhone or from the Apple Watch, and the strength trend, estimated maxes and plateau rule are all built from those two numbers. I would rather the app worked from what the bar did than from a rating that research says drifts by a rep, but if you want a per-set RPE column in your log, that is a real gap, and you should know about it before you choose.