RPE, or Rating of Perceived Exertion, is a way to measure how hard you’re working during exercise based on how your body feels rather than external numbers like heart rate or weight on a bar. There are two main versions: the original Borg scale (rated 6 to 20) used heavily in cardio and clinical settings, and a modified 1 to 10 scale popular in strength training. Both are simple to learn, but using them well takes a bit of practice and honest self-assessment.
The Two RPE Scales
The original Borg scale runs from 6 (no exertion at all) to 20 (maximum effort). The numbers seem odd, but they were designed to roughly correspond to heart rate when multiplied by 10. So an RPE of 13 (“somewhat hard”) suggests a heart rate around 130 beats per minute. A rating between 12 and 14 reflects moderate intensity, which is the sweet spot for most general fitness and cardio work.
Here’s how the Borg scale breaks down:
- 6: No exertion (sitting still)
- 9: Very light (easy walking)
- 11: Light (you could keep going for a long time with little effort)
- 13: Somewhat hard (breathing heavier, but you can still hold a conversation)
- 15: Hard (talking becomes difficult, you’re working noticeably)
- 17: Very hard (short phrases only, strong desire to stop)
- 19–20: Extremely hard to maximum effort (cannot maintain this for more than a short burst)
The 1 to 10 scale is more intuitive and dominates in weight rooms. In strength training, each number on this scale maps to “repetitions in reserve,” or RIR, which is how many more reps you could have done before failing. An RPE of 10 means you had zero reps left. An RPE of 9 means you could have done one more. An RPE of 8 means two more reps were possible, and so on down the scale. This connection between RPE and RIR is what makes the system practical for programming sets and reps.
How RPE Works for Strength Training
Most strength training programs that use RPE prescribe work in the 6 to 10 range. Here’s what each level means in practice:
- RPE 10 (0 RIR): You hit failure. You could not complete another rep with good form.
- RPE 9 (1 RIR): You stopped with one rep left in the tank.
- RPE 8 (2 RIR): You could have done two more reps. This is a common target for productive training that builds strength without grinding you down.
- RPE 7 (3 RIR): Three reps left. A good intensity for volume work or technique practice with meaningful load.
- RPE 6 (4 RIR): Four reps in reserve. Warm-up territory for heavy sets, or a recovery day intensity.
A program might say “3 sets of 10 at RPE 8–9.” That means you pick a weight where you finish each set of 10 with one or two reps still possible. If you could have done 4 more reps, the weight is too light. If you barely finished the tenth rep, you went too heavy. The beauty of this system is that it adjusts automatically to how you feel on a given day. If you slept poorly or are stressed, you’ll naturally use a lighter weight to hit the same RPE. If you’re feeling great, the weight goes up.
This flexibility is the core advantage. Consider that 83% of your one-rep max is roughly a 6-rep max. You could do 6 reps with zero reps in reserve, 5 reps with 1 in reserve, 4 reps with 2 in reserve, or 3 reps with 3 in reserve, and all of those represent approximately the same training load and intensity. RPE lets you match the effort to the prescription regardless of the exact weight.
How RPE Works for Cardio
For running, cycling, swimming, or any endurance work, the Borg 6–20 scale is more common. The simplest way to use it is the talk test. At an RPE of 11 to 13, you can hold a full conversation. At 15, you can manage short sentences. At 17 and above, talking is nearly impossible.
Most general fitness guidelines recommend training at an RPE of 12 to 16 for cardiovascular benefits. If you’re new to exercise or returning after a break, starting at 11 to 14 (light to somewhat hard) and gradually working up is a sound approach. Cardiac rehabilitation programs follow this same principle, beginning patients at an RPE of 11 to 14 and systematically increasing intensity until they’re consistently working at 12 to 16.
For interval training, you might alternate between RPE 15–17 during hard efforts and RPE 9–11 during recovery periods. For a long easy run, you’d stay at 11–13 the entire time. Matching your breathing and perceived effort to these numbers gives you a practical way to control intensity without constantly checking a watch or heart rate monitor.
Getting Better at Rating Yourself
The biggest challenge with RPE is accuracy, especially when you’re new to it. Research consistently shows that your ability to assess RPE improves with training experience. Novice lifters tend to overestimate how hard moderate loads feel and underestimate how much they have left at higher intensities. This isn’t a reason to avoid RPE. It just means you need a calibration period.
Start by rating every set or interval after you complete it, even if your program doesn’t require it. Write it down. Over the course of a few weeks, you’ll develop a more reliable internal gauge. Pay attention to specific body signals: how fast you’re breathing, how much your muscles burn, how quickly the bar slows down on the last few reps, whether you’re bracing or gritting your teeth. These physical cues anchor your subjective rating to something real.
Factors beyond the workout itself also shift your perception. Motivation, fatigue from previous sessions, sleep quality, caffeine intake, and even the temperature of the room all influence how hard something feels. This is actually a feature, not a bug. If heat and poor sleep make a weight feel like RPE 9 that normally feels like RPE 7, your body is telling you something useful. Respecting that signal is the whole point of autoregulation.
RPE vs. Fixed Percentages
Many programs prescribe weights as a percentage of your one-rep max (like “squat 80% of your max for 5 sets of 3”). RPE-based programs let you decide the weight based on feel. A natural question is whether one approach produces better results.
The research here is nuanced. A meta-analysis comparing autoregulated training to fixed-loading methods found that RPE-based programs produced similar strength gains to percentage-based programs. Neither approach was clearly superior for exercises like the squat, bench press, or deadlift. A different autoregulation method called APRE (which adjusts weight based on how many reps you complete in a test set) did show a meaningful edge over fixed loading, but standard RPE-based training was statistically equivalent.
This means RPE isn’t a magic shortcut to faster progress. Its real value is flexibility. Percentage-based programs assume your max stays constant between testing days, which it doesn’t. RPE accounts for day-to-day variation. It also simplifies programming when you don’t have a recent max to calculate from. For intermediate and advanced lifters, combining both approaches works well: use percentages as a starting point and RPE as a check on whether the prescribed weight matches your readiness that day.
Putting It Into Practice
If you’ve never used RPE before, the simplest way to start is to add it as a tracking tool alongside whatever program you’re already doing. After each working set in the gym, ask yourself: “How many more reps could I have done?” Write that number down next to your sets. After each cardio session, rate your overall effort on the 6–20 scale based on how hard you were breathing and how much you wanted to stop.
Within three to four weeks of consistent rating, most people develop a reliable sense of their own effort levels. At that point, you can start using RPE prescriptively. Instead of adding weight every week on a fixed schedule, you can target a specific RPE and adjust the load to match. On a good day, you lift heavier. On a rough day, you lift lighter. Both sessions count as productive training because the stimulus relative to your capacity stays consistent.
For strength work, RPE 7 to 8 is where most of your training volume should live. It’s hard enough to drive adaptation but leaves a buffer that reduces injury risk and allows you to recover between sessions. Reserve RPE 9 to 10 for testing days or peaking phases. For cardio, aim to spend most of your time at RPE 12 to 14 on the Borg scale, with occasional harder sessions pushing into the 15 to 17 range.