Rating of perceived exertion (RPE) can help you measure how hard your body is working when you exercise.
Using a scale from 6 to 20, you choose a rating number to describe how hard the activity feels. You base the number on how tired you are, how hard it is to breathe, and how hard it is to do the activity.
For most people, working at a moderate (RPE 12 to 13) to vigorous (RPE 14 to 17) level will help you get the most benefit from your exercise. If you have health problems, your RPE goal may be different. Talk with your doctor before you start an exercise program.
How hard do you feel the exercise is?
Very, very light
Very light (You feel comfortable.)
Somewhat hard (You feel tired but you can keep going.)
Very hard (You feel very tired, and you are pushing yourself to keep going.)
Very, very hard (This is like the hardest exercise you have ever done.)