RPE
RPE (rate of perceived exertion) is a 1–10 rating of how hard a set was. In lifting, it's scored by how many more reps you could have done: RPE 10 means none, RPE 9 means one, and RPE 8 means two. It lets you record and plan effort, not just weight.
Half-steps like 8.5 mean “definitely one more, maybe two”. For the percentage of your one-rep max that goes with each rating, see an RPE chart.
The general-fitness RPE scale you might know from cardio classes rates how hard your whole body is working, from breathing to heart rate. The lifting version was redefined in 2016 around reps left, because that's something a lifter can actually judge at the end of a set (Zourdos 2016).
They're the same measurement counted from opposite ends. RIR, reps in reserve, counts the reps you had left, and RPE = 10 − RIR. Programs and apps use one or the other. Once you know the conversion, it doesn't matter which.
It separates sessions that look identical. 100 kg × 5 at RPE 6 and 100 kg × 5 at RPE 9 look the same in a log without RPE. With it, the first tells you to add weight next time, and the second tells you to stay put.
It adjusts for the day. Your strength moves around with sleep, stress and fatigue. A program written as “5 reps at RPE 8” adjusts itself: on a good day that's more weight, on a bad day less. Adjusting training to the day like this is called autoregulation.
It controls fatigue. Most useful training happens at RPE 7–9. Taking every set to RPE 10 adds fatigue faster than it adds results.
Yes, with a caveat. Rating accuracy improves with experience. In the original study, experienced squatters rated sets more consistently than novices, and everyone was more accurate close to failure (Zourdos 2016). Across studies, people tend to underestimate how many reps they have left, by about one (Halperin 2022).
So beginners should log RPE from day one, since the habit is what matters, but not rely on it alone to choose weights for the first few months. If you rate a set RPE 8, you probably had closer to three reps left than two.
Picking a number from 1 to 10 between sets is a small chore, so Sweatora uses one tap per set: Easy, Good, Hard or Max. Those are stored as RPE 5, 7, 8 and 10. After the session, the app averages them per exercise to suggest your next weights.
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