The best and most accurate measurement for PD is received from your optometrist, and should be included in your prescription.
Why it is necessary to measure the Pupillary Distance(PD)?
How important it is to your vision, and why do you need it to buy glasses?
A growing range of the prescription lens has an "optical center" which is defined by the gap between the pupils. Pupillary distance is used to assess where your eyes are aiming through the lens of your glasses to be as precise as possible.
A pupillary distance measurement is necessary for properly fitting your eyeglass lenses. There is no reason to walk around with inaccurate glasses when it is so easy to get this number. Be sure to take your number, and the rest of your prescription, the next time you shop online for trendy eyeglasses.
How to measure your PD
Method 1 - Use A Mirror
Step 1. Position yourself approximately 8 inches (20cm) away from a mirror.
Step 2. Close your left eye and align the ruler’s zero to the center of your right pupil.
Step 3. Try not to move your head or the ruler. Close your right eye and note the reading directly over your left pupil. That will be your PD.
Step 4. You can also measure the distance from the outer rim of two pupils to verify the distance.
Method 2 - Ask a Family Member or Friend
Step 1. Look straight ahead with both eyes open facing your friend. Let the person hold the ruler up to your right so the zero end lines up with your pupil.
Step 2. Measure the distance from your right to your left pupil. The number that lines up with your left pupil is your PD
Step 3. Write the result down. To be certain of the result, let your friend measure a few more times to make sure your measurement is accurate.
Step 4. Repeat the process from right to left as well to confirm the measurement.
Method 3 - Use An App
Step 2. Follow the on screen instructions to obtain your PD
Step 3. Measure at least 3 times to verify the result