Measuring Pupillary Distance (PD) Using a Credit Card

PD is the distance between your pupils, and it's used to help center a prescription correctly in your frames. Credit cards have a globally standardized width of 85.60 mm and a height of 53.98 mm. Your interpupillary distance is calculated by detecting the size of the credit card in the image. The effective error of interpupillary distance is 2mm.

Our measurement results include both single-PD and dual-PD.

Credit card on the forehead
  • A broad forehead helps keep a credit card parallel to one's face.
  • It offers better tolerance for tilt angles (pitch).
  • Website visitors can press their credit cards against their foreheads without any hygiene concerns.
Credit card at the mouth
  • Holding the credit card close to mouth makes it more comfortable for hand, as it aligns with the body's natural structure.
  • In practice, it was observed that some website visitors—concerned about the hygiene of their credit cards—did not press the card firmly against their mouths, which led to significant measurement errors.
Video Tutorial
Online Demo
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Credit card at the forehead

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Credit card at the mouth

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