Pupil Distance or PD is the distance between the center of one pupil to the center of the other pupil. This measurement is used to correctly line up your prescription lens over your pupils. Your pupil distance is usually included on your prescription and can be in the range of 40 to 90. If you don't see your pupil distance on your prescription, you can request it from your doctor.
We recommend getting your PD measurement from your doctor, but there are apps for your phone that can help you measure your PD.