To calibrate your Wahoo Stride Sensor go to the workout settings -> foot pod sensor -> select the sensor you are using then you will be greeted by the initial stride sensor setup page where you can adjust the calibration value. The calibration factor represents a number that should be multplied by the footpod reported distance to get true distance. So if you ran 10 miles and the footpod reported 9.7. You would want to divide 10 by 9.7 and stick that in as the calibration factor 1.031. That is a typical error. If you are seeing much larger errors check that it is tight against your shoe and that it isn't crooked or backwards. If the calibration factor is entered manually, it will remember it and should take effect immediately.