RPE vs RIR: How to Estimate and Log Lifting Effort

RIR tells you how many more repetitions you think you could complete. RPE is a rating of perceived exertion; on the RIR-based scale used in lifting, RPE 8 means about two reps left, RPE 9 about one, and RPE 10 none. For hard lifting sets, they can describe the same estimate in different notation—not two competing training methods.

The important qualification is which RPE scale you mean. A general “how hard did that feel?” score is not automatically a count of remaining repetitions. This guide uses set-by-set, RIR-based RPE, not an aerobic or whole-session effort rating.

For generally healthy adults following a lifting plan, the useful question is: How do I record effort honestly, and what should I change when a set is harder than planned? You do not need to test a maximum or deliberately fail a repetition to start using an effort note.

RPE vs RIR: the useful conversion

For this part of the scale, RPE ≈ 10 − RIR is a useful translation. It does not make your estimate exact. Do not extend the subtraction into a precise prediction for every easy warm-up set; far from failure, “easy, several reps left” may be a more honest description.

A 2024 scoping review by Bastos and colleagues describes both direct repetitions-remaining scales and RIR-based RPE. It found these approaches useful for prescribing and adjusting resistance-training effort, with important limits to prediction accuracy. That supports using the scale as information, not treating a number as a measurement from a sensor.

Also, RPE 8 does not mean 80% of your one-rep maximum. The rating describes estimated effort at the end of that particular set; load and completed repetitions still need separate entries.

Count more of the same rep, not any rep you could force

At the end of a set, ask: “Without resting, how many more reps could I have done with the same range of motion and technique?” Then record your best estimate.

Keep that standard concrete. In a standing two-arm dumbbell biceps curl, extra reps that would require swinging your torso are not more of the same rep. In a flat dumbbell bench press, shortening the lowering range or getting help changes the task. Learn the movement and a safe way to finish the set before trying to judge its effort.

For this guide, the estimate always refers to repetitions meeting your established movement standard. Research definitions of task failure vary, which is one reason not to expect perfect agreement between every study or lifter.

Three distinctions help:

• A target is not a result. If your plan says 2 RIR but the set felt like no reps remained, log the actual estimate—not the target.
• Zero RIR does not require a failed attempt. It describes no further complete rep being available. Do not attempt another rep just to prove the label.
• A disrupted set may not deserve a number. If grip, balance, an unfamiliar setup or an interruption ended the set, write that down rather than pretending you know exactly how many reps remained.

Pain is not an effort target. Stop a movement that causes pain; stop training if you are dizzy or feel unwell. Persistent or concerning symptoms need appropriate professional assessment, not a different RPE score.

How accurate is the estimate?

Useful does not mean precise. An exploratory meta-analysis by Halperin and colleagues found that people were imperfect at predicting repetitions to task failure. On average, participants predicted fewer remaining reps than they could actually complete, but results varied substantially across studies. Training experience alone did not reliably explain accuracy.

Do not turn that average into a correction such as “always add one to your RIR.” Some sets and people will differ in the other direction. The review’s abstract also reported better accuracy with fewer repetitions and predictions closer to failure; that is a finding about measurement conditions, not advice to push every set to the limit.

The Bastos review likewise found accuracy limitations farther from failure and in higher-repetition sets. Its evidence came mostly from adult, resistance-trained samples, often small and male-only. Findings on whether experienced lifters estimate better than novices were mixed.

A practical way to use this uncertainty:

1. Keep familiar exercises, setup and range of motion reasonably consistent.
2. Record effort soon after the set, alongside the actual load and reps.
3. Use a range such as “about 2–3 left” when you cannot distinguish them. Do not invent decimal precision.
4. Note unusual rest, exercise order or technique changes before comparing sessions.
5. If you are new, treat the estimate as an extra note alongside your plan and technique feedback—not your sole reason to add weight.

This is a logging approach, not a validated method for eliminating estimation error. A qualified coach can help clarify the movement standard and how your program uses effort targets. There is no requirement here to run unsupervised failure tests to earn permission to use RIR.

A worked log: same reps, different decisions

Suppose your existing plan calls for two sets of 8–12 reps at about 2–3 RIR on the flat dumbbell bench press. These are illustrative entries, not a recommended starting load, a new workout or a prediction of progress.

The alternative equipment examples are 10 kg per hand or 20 lb per hand, not exact conversions. Rest and setup should follow your plan; record any meaningful change.

If the first set is already much harder than intended, do not force the second set to match it. Check readiness and rest, and reduce the load for remaining work if necessary to stay within your plan’s rep range and buffer. Record the changed load. End the set sooner if control or the intended effort limit arrives before the rep target.

A harder day does not, by itself, diagnose lost strength or inadequate recovery. Equally, the same reps at a lower reported RPE are an encouraging observation—not proof that you have gained a particular amount of muscle or increased your maximum by a calculable percentage.

For the next-session load decision, use the double-progression guide rather than adding weight solely because one effort score improved. If later sets repeatedly collapse, review rest between sets as well as the first set’s effort.

Which should you use—and how hard should you train?

Use the notation your program uses. If it asks for 2 RIR, write 2 RIR. If it asks for RPE 8 on the RIR-based scale, the intended buffer is similar. Recording both usually adds no information; translating the same estimate does not create a second independent measurement.

If you are choosing your own log format, “about two reps left” is a plain-language starting point. If a coach uses another RPE system, ask what its anchors mean instead of assuming this table applies.

Neither scale tells you what the program’s effort target ought to be. The 2026 ACSM overview of reviews supports resistance training without taking every set to failure, while noting insufficient evidence to specify exact RIR targets universally. A 2–3-rep buffer is a practical choice in our beginner full-body plan, not a uniquely proven optimum for every goal or exercise.

The website’s RPE calculator can compare estimated loads after you have a completed set to enter. It cannot verify your effort rating or turn an uncertain input into a reliable maximum. Its output is not a command to attempt a heavier lift.

The takeaway: choose one notation, keep the rep standard consistent, and record what happened rather than what was prescribed. An honest “not sure” is more useful than a precise-looking number that changes the next workout for the wrong reason.

Sources and scope

• Bastos, Machado and Teixeira, 2024: Feasibility and Usefulness of Repetitions-In-Reserve Scales for Selecting Exercise Intensity: A Scoping Review. DOI: 10.1177/00315125241241785. Full-text introduction, methods, results, discussion and conclusion consulted. Qualitative synthesis of 31 studies and 855 participants; not a trial proving one notation superior.
• Halperin and colleagues, 2022: Accuracy in Predicting Repetitions to Task Failure in Resistance Exercise: A Scoping Review and Exploratory Meta-analysis. DOI: 10.1007/s40279-021-01559-x. Abstract consulted. The meta-analysis included 12 studies with 414 participants and substantial between-study variation; its average error is not an individual correction factor.
• ACSM, 2026: Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews. DOI: 10.1249/MSS.0000000000003897. Full-text discussion of effort, failure, RIR targets and evidence limitations consulted. General healthy-adult guidance, not validation of the worked log.

The examples and logging decisions are practical editorial choices informed by this evidence, not personal training results, individualized coaching or a promise of progress.