RPE and RIR: how to use them to pick weights

RIR, or reps in reserve, is how many more clean reps you could have done when you ended a set. RPE, on the lifting scale, is the same idea counted down from 10: RPE 10 means no reps left, RPE 9 means one left, RPE 8 means two. To pick a weight, match it to the target. If the plan says 3 sets of 8 at 2 RIR, choose a weight you could lift about 10 times.

The scale

The reps-in-reserve version of RPE was described by Zourdos and colleagues in 2016. Each RPE point equals one rep left in the tank.

RPE	RIR	What it means
10	0	No more reps were possible
9	1	One more rep was possible
8	2	Two more reps were possible
7	3	Three more reps were possible
6	4	Moderate effort, four reps left
5 or below	5 or more	Easy, warm-up effort

Half points such as RPE 8.5 mean you are not sure whether one or two reps were left. Count only reps you could have done with the same form and range of motion. That is your technical limit, which on a heavy squat or bench often comes slightly before true failure.

Why use RPE or RIR at all

Your strength moves around from day to day with sleep, stress and food. A plan built only on fixed weights or percentages of an old max cannot see that. A target like “3 sets of 5 at 2 RIR” can. On a good day, you lift a bit more. On a rough day, you lift a bit less, and the effort stays where it should be.

It also controls how close to failure you train, which matters for both results and fatigue.

How accurate are you?

Not perfectly accurate, but accurate enough to be useful, and you get better with practice.

• A review and meta-analysis by Halperin and colleagues (2022), covering 12 studies and 414 participants, found that people underestimated how many reps they had left by about one rep on average, with a lot of variation. Predictions were more accurate closer to failure, with heavier loads, in sets of 12 reps or fewer, and in later sets.
• In a bench press study by Refalo and colleagues (2024), trained men and women judged 1 and 3 reps in reserve with an average error of well under one rep.

To calibrate yourself, now and then take the last set of a safe exercise to failure and compare it to what you predicted. Machines, cables and dumbbell curls are good for this. Never do it on a barbell bench press or squat without safety pins or a spotter.

How close to failure should you train?

Closer is not always better. A series of meta-regressions by Robinson and colleagues (2024) found strength gains were similar across a wide range of reps in reserve, while muscle growth improved somewhat as sets ended closer to failure. The authors called the analysis exploratory. A separate meta-analysis by Refalo and colleagues (2023) found no evidence that training to momentary failure beats stopping short of it for muscle growth.

A practical way to apply that:

Exercise type	Typical target	Why
Heavy squat, bench, deadlift	2 to 3 RIR (RPE 7 to 8)	Technique holds, fatigue stays manageable
Other compound lifts (rows, presses, lunges)	1 to 3 RIR (RPE 7 to 9)	Hard enough to grow, low risk
Isolation and machine work	0 to 2 RIR (RPE 8 to 10)	Low risk, and effort is easier to judge
Deload or technique sessions	4 or more RIR (RPE 6 or less)	Practice without adding fatigue

Using RIR to pick today’s weight

1. Warm up to the weight you expect to use, based on last session.
2. Do your first work set and rate it right away: how many more good reps could you have done?
3. Adjust the next set. If you had more reps left than the target, add weight. If you had fewer, take some off.

As a rough rule of thumb, each rep of difference is worth about 2 to 4% of the weight on sets of around 3 to 10 reps.

Example: the plan says squat 3 sets of 6 at 2 RIR.

Set	Weight	Rated RIR	Next step
1	100 kg (220 lb)	4	Two reps too easy, add 5 kg
2	105 kg (230 lb)	2	On target, stay
3	105 kg (230 lb)	1 to 2	Fine, start here next session

If set 1 had been a grinder at 0 RIR, you would drop to around 95 kg (210 lb) for the rest.

When you cannot change the weight

At home or in a hotel gym, the dumbbells may be fixed. Then reps do the adjusting instead of load. Keep going until you reach the target RIR rather than stopping at a set number. If the plan says 2 RIR and you stop at 12 reps with 2 left, that is your set. Write the reps down, and aim to beat them next time at the same effort. Once a set runs past about 20 reps, switch to a harder version of the exercise, such as single-leg work or a slower lowering phase.

Using RIR to progress over a block

RIR works well with double progression. Keep the reps fixed and let the target effort climb across a block, adding a little weight each week to match. Then ease off.

Week	Sets and reps	Target RIR	RPE
1	3 sets of 8	3	7
2	3 sets of 8	2	8
3	3 sets of 8	1	9
4	2 sets of 8, lighter	4	6

Your log also tells you when you have got stronger. If a weight that rated 1 RIR a month ago now rates 3 RIR, the same weight has become easier, and you can move up.

Common mistakes

• Rating how tired you feel instead of reps left. A set of 15 can feel brutal and still have three reps in it. The question is only how many more reps you could have done.
• Guessing loosely on high-rep sets. Estimates are least accurate far from failure and on sets above about 12 reps. Be honest with yourself on those.
• Rating before the set is over. Rate the moment you rack the weight, not halfway through.
• Pushing to RPE 10 on lifts where form breaks first. On heavy barbell lifts, your limit is the last rep with good technique.
• Writing the number down and never using it. RPE only helps if it changes your next set or next session.

Pain is not effort. If a lift hurts, stop and see a physical therapist or doctor.

How RepChief helps

RepChief logs every set with your history and personal bests, so you can see what you lifted last time before you pick today’s weight. With RepChief Pro, Chief reads the sets you log and can adjust your plan as your lifts move. His weight suggestions are advice, and you decide what goes on the bar.