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The frame pupillary distance, or frame PD, is the distance from the center of one lens opening in an eyeglass frame to the center of the other. It is a fixed measurement of the frame itself, not a measurement of your eyes. This number is used along with your personal pupillary distance to make sure your prescription lenses are fitted correctly.
read more about frame pupillary distance pd ...The frame PD is easy to calculate using the numbers printed on the frame's arm. It is the eye size plus the bridge size. For example, if a frame is marked with the numbers 52-18-140, the eye size is 52 mm and the bridge size is 18 mm. You would add these together (52 + 18) to get a frame PD of 70 mm.
It is important to understand the difference between these two numbers. Your personal PD is the distance between the pupils of your eyes, which is a measurement of your face. The frame PD is the distance between the centers of the frame's lenses. The frame PD will almost always be wider than your personal PD because of how glasses are designed to fit.
The difference between the frame PD and your personal PD tells the optical lab how much to decenter, or shift, the lenses inward. The goal is to line up the optical center of each lens with the center of your pupil. For example, if the frame PD is 70 mm and your PD is 64 mm, each lens must be shifted inward by 3 mm. This step is necessary for clear and comfortable vision.
The Frame PD creates a fixed, symmetrical reference point which is the exact center of the glasses. However, human faces are rarely perfectly symmetrical. Your nose might be slightly to the left, or one eye might be further from your nose than the other. By comparing your specific "monocular PD" (the distance from the center of your nose to each pupil) against the fixed Frame PD, the lab ensures that each lens is customized to your unique facial asymmetry.
No, you should not try to match these numbers. The frame PD will be wider than your personal PD. An optician will help you choose a frame where the difference is not too large, which helps keep your lenses as thin and light as possible.
No. The frame PD is just the distance from the center of one lens to the center of the other. The total width of the frame is a larger number because it includes the outer edges of the lenses and the endpieces.
Yes. Most online retailers list the eye size and bridge size for their frames. You can simply add these two numbers together to find the frame PD.
You do not need to worry about calculating the frame PD yourself. Your optician will handle all the necessary measurements to ensure a perfect fit. However, if you have a strong prescription, you can talk to your optician about finding a frame with a PD that is a good match for yours. This will help you get the best possible cosmetic result for your lenses.
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5 Signs Your Glasses Don't Fit. All About Vision. https://www.allaboutvision.com/eyewear/eyeglasses/fit/wrong-size-glasses/. Accessed April 3, 2026.
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