What does RPE 8 mean in lifting?

RPE 8 means you finished the set with about 2 good reps left in the tank. It is a common target for strength and muscle work because it is hard but leaves you able to train again soon.

Is RIR the same as RPE?

They measure the same thing from opposite ends. RIR is the number of reps you had left; RPE is 10 minus that. So 2 RIR is RPE 8, and 0 RIR is RPE 10.

What RPE should I train at to build muscle?

Most sets at RPE 7 to 9, meaning 1 to 3 reps left. Growth improves as sets get closer to failure, but stopping 1 to 2 reps short builds as much muscle as going to failure, with less fatigue.

Are people accurate at rating RPE?

Fairly. Across 12 studies, lifters underestimated the reps they had left by about one on average, and were more accurate close to failure and on sets of 12 reps or fewer.

Can I use RPE to estimate my one-rep max?

Yes. Add the reps you did to the reps you had left, then use a formula such as Epley: max = weight x (1 + reps to failure / 30). The RPE calculator does this for you.

Is RPE good for beginners?

Beginners can use it, but ratings are less reliable far from failure. A simple plan that adds weight each session works well at first, with RPE added once you know what a hard set feels like.

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RPE and RIR explained

Reviewed by Aaron Parry, strength and conditioning coach for RAF Rugby and Peterborough Rugby
Updated 26 October 2026

8 min read6 sources citedEditorial standards

In lifting, RPE (rating of perceived exertion) scores how hard a set was from 1 to 10, and RIR (reps in reserve) is how many more good reps you could have done. They are two sides of one scale: RIR = 10 minus RPE. A set at RPE 8 means you stopped with about 2 reps left; RPE 10 means you could not have done another rep. Most strength and muscle work sits between RPE 7 and 9.

The RPE scale for lifting

The lifting RPE scale most coaches use ties each number to reps left in the tank. It was set out by Mike Zourdos, Eric Helms and colleagues, who showed that experienced squatters' ratings tracked bar speed closely: the slower the rep, the higher the RPE (Zourdos et al., 2016).

RPE	Reps in reserve (RIR)	What it feels like
10	0	Maximum. No more reps, and no more weight.
9.5	0 to 1	No more reps, but you could have added a little weight.
9	1	One more rep was there.
8.5	1 to 2	Definitely one more, maybe two.
8	2	Two more reps left.
7.5	2 to 3	Two more for sure, maybe three.
7	3	Three more reps left. Bar still moving quickly.
5 to 6	4 to 6	Comfortable. Warm-up or technique work.

Half points (8.5, 9.5) are for sets where you are honestly not sure. Below RPE 7, a number is a rough label rather than a precise count.

RPE vs RIR: which should you use?

They carry the same information, so use whichever you find easier. Many lifters find RIR more natural ("I had two left") and many programmes write RPE ("3 x 5 at RPE 8"). The maths to switch between them is just RIR = 10 - RPE. In Lift Proven you rate a finished set from 7 to 10, and the app reads 8 as "2 reps left".

Note that the lifting scale is not the same as the 6 to 20 Borg scale used for cardio. If a sports scientist asks for your RPE after a run, they mean something different.

How accurate are lifters at rating sets?

Better than guessing, but not perfect. A 2022 meta-analysis pooled 12 studies (414 people) where lifters predicted how many reps they had left and then went to failure. On average they underestimated by about one rep, and they were more accurate when the set was close to failure and when the set was 12 reps or fewer. Training experience made little difference to accuracy (Halperin et al., 2022).

Three practical points follow:

Ratings near failure are the most trustworthy. An RPE 9 is a better guide than an RPE 6.
High-rep sets are hard to judge. On a set of 20 leg presses, burning legs make it feel closer to failure than it is.
Calibrate now and then. Take an occasional last set to a safe failure (a machine, or a bench with safeties) and compare it with what you would have rated. It teaches you what RPE 9 really feels like.

RPE and percentages of your max

Reps and RPE together tell you roughly what percentage of your one-rep max a set was. A set of 5 at RPE 8 means you could have done about 7 reps, which is a weight of about 81% of your max using the Epley formula. That is how the RPE calculator turns any rated set into an estimated max and a full chart of weights.

Reps	RPE 10	RPE 9	RPE 8	RPE 7
1	100%	94%	91%	88%
3	91%	88%	86%	83%
5	86%	83%	81%	79%
8	79%	77%	75%	73%
10	75%	73%	71%	70%

These come from the Epley formula, max = weight x (1 + reps to failure / 30), with reps to failure = reps done + reps in reserve. Published RPE charts from coaches differ by a per cent or two, and some lifters get more or fewer reps at a given percentage than the formula expects. Treat the chart as a starting point and let your own logs correct it.

Does training by RPE work?

Yes. In an 8-week study of trained men, one group lifted set percentages of their max and the other picked loads to hit target RPEs, with sets and reps matched. Both gained strength and muscle, with no significant difference between groups, and the RPE group showed a small, likely strength advantage on the squat (Helms et al., 2018). The appeal is that RPE adjusts for the day: if you slept badly, the same RPE 8 gives you a lighter weight automatically.

What RPE should you train at?

For muscle: growth improves as sets end closer to failure (Robinson et al., 2024), but you do not need to hit failure. Trained lifters stopping 1 to 2 reps short grew as much as those going to failure (Refalo et al., 2024). Aim for RPE 7 to 9 on most sets, with the last set of an isolation exercise up to RPE 9.5 or 10.
For strength: strength gains were similar across a wide range of effort in the 2024 analysis. In one 5-week study of trained lifters, sets ending at 0 to 1 RIR and at 4 to 6 RIR on the squat, bench and deadlift gave no significant differences in strength or muscle size (Ruple et al., 2023). Heavy compounds at RPE 7 to 9 are plenty, and they leave you fresh for the next session.
For technique and warm-ups: RPE 5 to 6.

How to start using RPE

After each working set, ask "how many more clean reps could I have done?" Write the answer as RIR, or 10 minus it as RPE.
Rate straight away, before the next set. Memory makes sets seem easier than they were.
Count only reps with full range and good form. A grinding rep with your hips shooting up does not count as "one more".
Use the rating to set the next session: if 3 x 5 was meant to be RPE 8 and felt like 6, go up more than usual. If it felt like 9.5, hold the weight.

How Lift Proven uses RPE

Rating sets in Lift Proven is optional. After a working set on the big lifts and their close variations, you can tap how hard it felt from 7 to 10. A rated set sharpens your estimated max, because the app knows how many reps you had left. Over time it also compares your ratings with your all-out sets, so if you usually have a rep more in the tank than you say, it tells you and allows for it. The coach then sets every weight, set and rep for your next session.

Rate your sets, and let the coach do the rest

Tap how hard a set felt and Lift Proven sharpens your estimated max, learns how accurate your ratings are, and sets your next session from it.

Download on the App Store Coming soon to Google Play

Questions

What does RPE 8 mean in lifting?: RPE 8 means you finished the set with about 2 good reps left in the tank. It is a common target for strength and muscle work because it is hard but leaves you able to train again soon.
Is RIR the same as RPE?: They measure the same thing from opposite ends. RIR is the number of reps you had left; RPE is 10 minus that. So 2 RIR is RPE 8, and 0 RIR is RPE 10.
What RPE should I train at to build muscle?: Most sets at RPE 7 to 9, meaning 1 to 3 reps left. Growth improves as sets get closer to failure, but stopping 1 to 2 reps short builds as much muscle as going to failure, with less fatigue.
Are people accurate at rating RPE?: Fairly. Across 12 studies, lifters underestimated the reps they had left by about one on average, and were more accurate close to failure and on sets of 12 reps or fewer.
Can I use RPE to estimate my one-rep max?: Yes. Add the reps you did to the reps you had left, then use a formula such as Epley: max = weight x (1 + reps to failure / 30). The RPE calculator does this for you.
Is RPE good for beginners?: Beginners can use it, but ratings are less reliable far from failure. A simple plan that adds weight each session works well at first, with RPE added once you know what a hard set feels like.

References

Zourdos MC et al. Novel resistance training-specific rating of perceived exertion scale measuring repetitions in reserve. Journal of Strength and Conditioning Research, 2016. doi:10.1519/JSC.0000000000001049
Halperin I et al. Accuracy in predicting repetitions to task failure in resistance exercise: a scoping review and exploratory meta-analysis. Sports Medicine, 2022. doi:10.1007/s40279-021-01559-x
Helms ER et al. RPE vs. percentage 1RM loading in periodized programs matched for sets and repetitions. Frontiers in Physiology, 2018. doi:10.3389/fphys.2018.00247
Robinson ZP et al. Exploring the dose-response relationship between estimated resistance training proximity to failure, strength gain, and muscle hypertrophy. Sports Medicine, 2024. doi:10.1007/s40279-024-02069-2
Refalo MC et al. Similar muscle hypertrophy following eight weeks of resistance training to momentary muscular failure or with repetitions-in-reserve in resistance-trained individuals. Journal of Sports Sciences, 2024. doi:10.1080/02640414.2024.2321021
Ruple BA et al. The effects of resistance training to near failure on strength, hypertrophy, and motor unit adaptations in previously trained adults. Physiological Reports, 2023. doi:10.14814/phy2.15679