When you have finished an ophthalmic examination or vision test, doctors will write your PD on the prescription. Generally, there are two different PD values.One of them is your basic PD, which is the distance in MM between the centers of your pupils. The other is mono PDs (PD for each eye), two numbers around 30mm. If you don't have any PD values on the prescription, you have rights to contact your doctor/optometrist from whom you received the prescription to get your accurate PD value.
You can ask help from a family member or a friend and let her/him measure out your PD by following the measurements below:
Both of you should sit down approximately 43cm (17 inches) away from each other. The person having his/her PD measured needs to keep both eyes open.
Place a simple mm ruler on your nose so that the starting point of the ruler is exactly at your left or right eye pupil. Keep the scale straight.
Make Sure to look straight
Stand in front of the mirror or ask one of your friend to read the scale to measure the distance between the pupils.
Repeat this at least three times to be more accurate.