# What do reps in reserve tell you about a set? Reps in reserve, or RIR, is your estimate of how many more complete repetitions you could have done before you had to stop. If you finish eight squats and think two more good squats were possible, you might record two RIR. It is a practical way to describe set effort. It does not tell you exactly how much weight you can lift, and it is not a reason to test failure in every set. ## Count only good repetitions When you estimate RIR, think about repetitions with the same useful range and control. If you could lift the weight three more times only by shortening the movement or swinging, those do not count as three good repetitions left. This distinction keeps the estimate tied to the exercise you planned. The [Mayo Clinic technique guide](https://www.mayoclinic.org/healthy-lifestyle/fitness/in-depth/weight-training/art-20045842) asks for controlled lifting and lowering, which gives you a clear standard for the estimate. If a set ends because your grip slips, a machine part shifts, or you feel sharp pain, RIR may not be meaningful. Record the reason the set ended. Do not try to guess how many repetitions your muscles could have done under a different setup. Fix the setup or seek advice first. ## Read what a low or high number means Zero RIR means you believe another full repetition was not possible. One RIR means one more may have been possible. Four or five RIR means the set was well short of that point. A [paper on RIR-based RPE](https://pubmed.ncbi.nlm.nih.gov/27531969/) describes using this estimate to judge training effort. The number can help you choose a load and compare sessions. It is not a score you need to make as small as possible. A beginner may use more repetitions in reserve while learning an exercise. A harder working set can use fewer. The right amount depends on the goal, the lift, and how much training you can recover from. A [review of training to failure](https://pubmed.ncbi.nlm.nih.gov/33497853/) found no clear need to take every set to failure for strength and muscle growth in the studies reviewed. Leaving some good repetitions possible is a valid choice. ## Use it to choose the next load Suppose your plan calls for eight to twelve repetitions. You do eight rows and estimate six more good repetitions were possible. You may need a higher load for a challenging working set. Try a small increase after rest, then check whether the movement stays the same. If you do eight and estimate only one more possible, you may keep the load. If the plan asked for an easier day, you may lower it. For a split squat, balance may be the limit before leg effort. You might finish six and feel the leg could do many more, but you wobble. Do not use that RIR estimate to justify heavier dumbbells. Make the setup steadier or use a support first. RIR is useful only when it describes the effort that actually limits the set. ## Accept that the estimate is rough People do not always predict the exact number they could do. A [study of prediction accuracy](https://pubmed.ncbi.nlm.nih.gov/29204323/) found that estimates were not perfect and tended to improve with training experience. It is often easier to tell “many left” from “almost none” than to separate exactly two from three. You can use broad categories in your first weeks. “About two to four RIR” may be more honest than a precise number. You can also compare later sets. If the same load gives ten repetitions with about three RIR in set one and only seven with about one RIR in set three, the work became much harder. That may be expected. Record the pattern rather than forcing all three sets to match the first. ## Use the estimate in a training log One useful check is to compare the estimate with your next planned set. If you wrote “five RIR” after set one but cannot reach the same count after normal rest, the first estimate may have been too high. You do not need to test failure to learn from this. Revise the estimate and keep the load steady until the pattern is clearer. Record weight, repetitions, and RIR in Helios or a notebook when it helps you make a decision. “Goblet squat: 12 kg × 10, about 3 RIR” gives enough detail to compare later. If you repeat the same setup for ten reps and estimate more repetitions left next month, the load may have become easier for you. You might add a repetition or try a small weight increase. Do not let RIR replace the basics: choose a safe setup, move through a useful range, and stop for pain or loss of control. It is an estimate of effort, not a measure of technique or health. Use it to make small adjustments, and let repeated sessions show whether your choice worked. ## Sources * [Helms et al.: Application of RPE for Resistance Training](https://pubmed.ncbi.nlm.nih.gov/27531969/) * [Grgic et al.: Failure versus non-failure resistance training](https://pubmed.ncbi.nlm.nih.gov/33497853/) * [Steele et al.: Ability to predict repetitions to failure](https://pubmed.ncbi.nlm.nih.gov/29204323/) * [Mayo Clinic: Weight training technique](https://www.mayoclinic.org/healthy-lifestyle/fitness/in-depth/weight-training/art-20045842) Updated: 2026-10-18 ## Guide topics - [Strength training guides](/blog/topics/strength-training/index.md) ## Related guides - [What does RPE mean in a workout log?](/blog/rpe-in-workout-log.md): Read a set effort rating and use it beside weight and repetitions. - [How do you estimate effort on a new exercise?](/blog/estimate-effort-new-exercise.md): Use a light test set and broad effort words while you learn a new lift. - [How do you choose a load for a target rep range?](/blog/choose-load-for-target-rep-range.md): Test a manageable weight and match it to the repetitions you plan to do. - [How do you record effort when every set feels different?](/blog/record-effort-different-sets.md): Log each set as it happened and use the pattern to choose your next workout.