RPE vs RIR: what reps in reserve means and how to use it

RIR (reps in reserve) is how many more reps you could have done when you racked the bar. RPE (rating of perceived exertion), on the scale lifters use, is 10 minus RIR. RPE 8 means two reps left and RPE 10 means none, so they are one scale. Lifters misjudge it by about a rep, and by less the closer they get to failure.

RPE vs RIR: how the two scales convert

Zourdos and colleagues built the scale in 2016 by tying each RPE score to a count of reps left. Helms and colleagues wrote up how to program with it the same year.

Below RPE 7 the scale uses ranges: RPE 5 to 6 covers 4 to 6 reps left.

Charts and programmes also use half points. RPE 8.5 sits between one and two reps left, which a whole-number RIR can only round one way or the other. Programmes written in RIR usually give a range instead, and "RIR 1 to 2" asks for the same effort as RPE 8.5.

RPE 8 and RIR 2 ask for the same set. Use whichever your programme is written in.

How accurate is RIR?

Across 12 studies and 414 people who guessed how many reps they had left and then kept going until they could not do another, the guess came in 0.95 reps short on average (Halperin 2022). People had more left than they thought, and the studies disagreed a lot with each other. Guesses got slightly better near failure and in sets that failed within 12 reps, and training status made no measurable difference.

Another review found the error grew with distance from failure (Hackett 2017). Lifters with 0 to 5 reps left were off by about one rep, and with 7 to 10 left, by more than two.

In one bench press study, 24 resistance-trained men and women pressed 75% of 1RM, and their estimates were off by 0.65 reps on average (Refalo 2024). Estimates of 3 reps left were as good as estimates of 1. All of them were trained, and it was one lift.

Practice did not help in one small study. Nine trained men benched three times a week for six weeks and estimated their reps left during their sets. At the end they were no more accurate than at the start (Remmert and colleagues, 2023).

A rep either way is close enough to set a load by.

How close to failure to train in the first place, and what the reviews say about stopping short, is in Training to failure.

Turning RIR into a load

Add RIR to the reps you did and you have the reps you could have done, which a 1RM formula turns into a share of your max. That is the calculator's method. Povver's own weekly estimate skips the RIR step, as the last section explains. The RPE calculator uses Epley's formula: 5 reps at RIR 2 counts as 7 to failure, about 81% of 1RM.

Real lifters do not follow these charts exactly. Pooled studies of reps to failure at a fixed percentage of 1RM (Nuzzo 2024) found that at 80%, lifters managed 9.75 reps on average, and individual lifters typically differed from that by about 2.5 reps. Exercise matters too: the leg press ran to more reps than the bench press at every load, 13.1 against 8.8 at 80%. Helms and colleagues say as much about their own RIR chart, which should not be viewed as "an absolute conversion tool".

So treat the chart as a starting weight and adjust from the RIR your sets actually come in at. If you want a max from a single set, the 1RM calculator gives a likely range beside the number.

How to use RIR to pick a load and add weight

Pick a target. Povver's judgment is that one to three reps in reserve on most working sets is a workable range. No review we know of names a range, and Training to failure has the evidence. Far from failure the rating means less: an RIR of 5 mostly says the weight was light.

Set the load on the first set. Choose a weight that leaves your target on the first working set and keep it for the rest. As a rule of thumb, if a set ends three or more reps better than planned, the weight was too light. Raise it for the next one.

Add reps first, then weight. Take a range of 8 to 12 reps and a target of RIR 2. Add a rep each session a set reaches its rep target at RIR 2 or easier. Add weight once the last set reaches 12 at RIR 2 or more. The reps usually dip after the jump and then climb again. Double progression has the full rule, and Progressive overload places it among the other levers, and progression models compared sets it beside linear and percentage-based loading.

Judge it by the bar and by form. In 29 squatters, the slower the bar moved, the higher they rated the set, and the link was strong in both experienced lifters and novices (Zourdos 2016). Form is the other cue. It often starts to go on the last rep or two.

Does loading by effort work? In an 8-week trial (Helms 2018), 21 resistance-trained men trained squat and bench press, one group with loads set by percentage of 1RM and one choosing loads to hit a target RPE. Both groups gained strength and muscle thickness, and the differences between groups were not significant. The authors saw a possible small strength edge for the RPE group. A review of 14 studies of effort-based loading with 356 participants (Larsen 2021) found 1RM rose in every protocol, and the authors suggest RIR-based RPE can be an effective method.

How Povver uses RIR

Povver, a strength training app, asks for RIR, 0 to 5, on every working set. It sits in the set grid beside weight and reps, pre-filled from your plan or your last session. Touch it only when a set felt different. Povver works out its weekly estimated 1RM from the reps you did, not the reps you had left. RIR instead sizes the next jump in weight.

Which sets count. By Povver's convention, a hard set is a working set finished at RIR 3 or lower, and weekly volume per muscle counts hard sets. An easy set at RIR 5 adds nothing. A set logged without RIR counts as hard.

When the weight goes up. Every set in your plan has a target RIR. When a set reaches its rep target at that effort, its target goes up a rep next session, or by up to three reps if you had more in reserve. The weight goes up after one session in which you finish every working set and your last set would have reached the top of the range at your target RIR, so on an 8 to 12 range with a target of RIR 1, 11 reps at RIR 2 counts as 12. The step is at least one increment and no more than 10% of the load (5% on isolation lifts), and with no RIR logged it takes two sessions in a row at the top.

A working set that lands more than a rep harder than planned keeps the weight where it is, and a repeat at that weight drops it a step. Two or more reps below the range drops it next session. Double progression and how it works have the full rule.

Lifters tend to under-report reps left, so a wrong rating more often keeps the weight where it is than raises it too soon.

RIR: common questions

What does RIR mean?

RIR stands for reps in reserve: how many more reps you could have done with good form when you ended a set. RIR 0 means you reached failure, and RIR 2 means two more reps were there.

Is RIR 0 the same as failure?

Yes. RIR 0 means no more reps were left when the set ended, which is failure.

What is the difference between RIR and RPE?

They are one scale written two ways. On the lifting RPE scale, RPE equals 10 minus RIR, so RPE 8 is 2 reps in reserve and RPE 10 is none (Zourdos 2016).

What is a good RIR for building muscle?

One to three reps in reserve on most working sets is a workable range, in Povver's judgment. No review we know of names a range, and muscle size tends to grow more the closer sets end to failure.

How accurate is your RIR?

About a rep off, on average. Across 12 studies, lifters had 0.95 reps more left than they predicted (95% CI 0.17 to 1.73), with better accuracy close to failure (Halperin 2022).

How do you use RIR to add weight?

Add reps first at a set target RIR, then add weight once the last working set reaches the top of the rep range at that RIR or easier. Reps usually dip after the jump and then climb again.