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PD (Pupillary Distance): What it Means
Knowing your PD (distance between the centers of your pupils) is just as essential as your prescription when crafting eyeglasses customized for you. Using your PD measurement, Optical Lens Lab aligns the optical center of your lenses to each pupil to ensure comfortable vision at all distances.
Single PD vs. Dual PD
It’s important to know that either a single or a dual PD is acceptable for making glasses. They are just two different ways of measuring the same thing.
A single PD is the measurement (in millimeters) between eyes from pupil center to pupil center.
A dual PD is the measurement (in millimeters) from the center of your nose to each pupil center. In this case, the first number is the right eye (OD) to bridge center and the second number is the left eye (OS) to bridge center.
PD on an Eyeglass Prescription
Sometimes your eye doctor will include the PD measurement on your prescription. An adult’s single PD will usually be a number in the mid-50s to 70s, whereas a child’s PD will be mid-40s to high 50s. Dual PD numbers will each be approximately half of those numbers.
If your eye doctor didn’t provide your PD measurement on your prescription, follow the instructions below to measure it yourself.
How to Measure PD (Pupillary Distance)
Method 1: Look in a Mirror
• Millimeter Ruler
Need a millimeter ruler? Download and print one using the link here. Be sure to print it at actual size.
- Stand 8 inches in front of the mirror, looking straight at it.
- Hold the ruler horizontally and level above your eyes.
- Determine your PD measurement:
- Close your right eye
- Line the zero on the ruler to the center of your left pupil
- Open your right eye
- Measure the distance from the center of your left pupil to the center of your right pupil
Tips if you recruit a friend to help you read the ruler measurement:
- Have your friend crouch or sit in front of you
- Look above your friend’s head — not at your friend — at an object straight across the room from you
- Keep your eyes still and facing forward
Method 2: Mark Your Glasses
- Millimeter Ruler
- Non-permanent felt tip marker
If you do not have a millimeter ruler, you can download and print one using the link here. Be sure to print it at actual size.
- Choose an object that is 20 feet away from you.
- Focus on that object. Point your nose at the object so each eye is equidistant from it.
- With the felt tip marker, make a dot where the object appears on your left and right lenses. The dots should appear as one to cover the object you’re focusing on.
- Use a millimeter ruler to measure the distance from the centers of the marker dots to one another.
When finished, wash your lenses with water and gentle soap, if necessary. Do not use anything harsh, such as rubbing alcohol.