Rating of perceived exertion (RPE) can help you measure how hard your body is working when you are exercising.
Using a scale from 6 to 20, you choose a rating number to describe how difficult the activity feels based on how tired you are, how difficult it is to breathe, and how hard it is to do the activity.
For most people, exercising at a moderate (RPE 12 to 13) to vigorous (RPE 14 to 17) level will help you get the most benefit from exercising. If you have health problems, your RPE goal may be different. Talk with your doctor before starting an exercise program.
How hard do you feel the
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 continue)
Very, very hard (the most difficult exercise you have ever done)