How to Measure Your Pupillary Distance
What is PD?
PD stands for Pupillary Distance, which is the measurement from the center of one pupil to the center of the other. Your PD is an important factor and tells you where you look through the lens of your glasses and should be as accurate as possible. For people with strong prescription, this is especially important. You can normally find your PD on your prescription. Generally speaking, the PD numbers for adults stays the same. The average PD range for adults is 57-72 mm and for kids is about 43-58 mm.
Your PD may be written in three ways:
1.Binocular PD is notated as a single number such as "63", means the total distance between your pupils.
2.Monocular PD is the distance from the bridge of your nose to your pupil on each side. It is notated as two numbers around 30mm such as 31 and 32.
3.Sometimes PD is notated as "61/58". 61 is your distance PD which can be used when you need single vision distance glasses, bifocal and progressive glasses. While 58 is your reading PD which can only be used when you need single vision reading glasses. (The reading PD is normally 3mm less than the distance PD as eyes will get closer when reading.)
Please keep in mind that the PD is not always given as part of your prescription when you have an eye exam. If it’s missing, don’t worry, we can help.
How to measure PD
Measuring your PD can be done easily at home, especially with a friend, or a family member. If you are wearing glasses, remove them and look at something 10-20 feet away.
Have your friend hold the PD ruler over your eyes while placing the zero to the center of your right pupil. Read the measurement. The number directly over the center of your left pupil is your PD. Have your friend repeat the measurement a few times to make sure it’s correct.
It is also easy to measure your PD all by yourself. All you need is your PD ruler and a mirror.
1. Fold your PD ruler so that the side labeled “using a mirror” is facing out.
2. Stand about 8 inches or 20 cm away from a mirror.
3. Hold the ruler over your eyes. And keep the zero over your left pupil.
4. Close your left eye, and open your right eye while looking straight. The number directly over your right pupil is your PD.
Note that: For reading glasses, you can deduct 3mm from your PD measurement.
For additional information, please check out our guides.