How to Measure Your PD

Learn how to get a precise Pupillary Distance (PD) measurement from home using our AI sizer tool. Fully updated with card and card-less techniques.

Your Pupillary Distance (PD) is the physical distance in millimeters between the centers of your pupils. It is a vital measurement when ordering prescription glasses online, ensuring that the optical center of the lenses aligns perfectly with your visual axis. Our tool supports two calibrated methods of measurement: Card Mode and Card-less Mode.

Touch-Precision Helper Features (Built for Mobile)

🔍 Zoom Loupe

When dragging sizers on touchscreens, a 2.5x circular magnifying glass floats offset above your finger so you can center pupil points down to the exact pixel.

🕹ī¸ Nudge Arrows

Use our pixel nudge arrow pad to move active sizers by exactly 1 pixel in any direction, providing hassle-free alignment without dragging.

📐 Monocular Split

Calculates both Binocular PD and Monocular PD (Left/Right split from nose bridge) using vector projection to compensate for minor head tilts.

What You Need

1. Device

A webcam-enabled smartphone, tablet, or laptop. Ensure you stand in a bright, evenly-lit room.

2. Scale Card

*(For Card Mode only)* A credit card, library card, or any plastic magnetic-strip card. We use its standardized 85.6mm width as scale.

3. Iris Contrast

*(For Card-less Mode)* Natural light or front-facing lighting so the boundary of your irises (the colored part of your eyes) is clearly defined.

Method 1: Card Reference Mode

Uses a physical card held against your face to define absolute millimeter ratios.

1

Align Your Card

Hold a credit card directly under your nose, flat against your upper lip. Hold it by the bottom corners so your fingers don't block the card edges. Keep it perfectly horizontal.

2

Capture Portrait

Align your head inside the dotted oval webcam template and press Capture Photo (or upload an existing photo of yourself).

3

Adjust Pupils & Card Edges

The AI will automatically place markers on your pupils and nose bridge. Drag the markers to refine their centers, then drag the green markers to align exactly with the left and right edges of the card.

Method 2: Card-less (Iris Calibration)

Uses the anatomical standard horizontal width of the adult iris (11.7mm) to scale measurements.

1

Align Your Face

No cards or objects are needed. Simply position your face in front of the camera, looking straight into the lens. Ensure your eyes are open and brightly lit.

2

Verify Pupil Centers

Capture your portrait. Drag the red dots if they aren't centered exactly over the dark pupils of both eyes.

3

Align the Iris Rings

Adjust the Iris Calibration Slider below the canvas. This changes the size of the dotted blue rings. Align the rings so they wrap exactly around the outer edge of your colored irises to calibrate the scale!

🌟 Pro Tips for Maximum Accuracy

  • Remove Glasses: Glasses frame edges and reflections can interfere with both AI eye detection and your manual alignment.
  • Look at the Lens: Always look directly into the camera lens (not at your face on the screen) to ensure your pupils are perfectly centered horizontally.
  • Privacy Card Cover: When using Card Mode, you can hold the card with the magnetic strip facing forward or cover your personal card details. We only analyze the outer width bounds of the card shape.