What is pupillary distance (PD)?
Pupillary distance (PD) is the distance between the centers of your two pupils, measured in millimeters. When a lab makes your glasses, it uses your PD to place the optical center of each lens exactly in front of each pupil.
Why it matters
Lenses bend light. Look through a point away from the optical center and you get a prism effect - the image shifts slightly. If your lenses are made with the wrong PD, your eyes constantly compensate for that shift, which can mean eye strain, headaches, or blurry edges. The stronger your prescription, the more a wrong PD hurts.
Average PD values
| Group | Typical range | Most common |
|---|---|---|
| Adults overall | 54–74 mm | 60–66 mm |
| Adult women | 54–68 mm | ~62 mm |
| Adult men | 58–72 mm | ~64 mm |
| Children | 43–58 mm | grows with age |
These are population ranges, not targets - your own measured value is what belongs on the order form.
Single PD vs dual PD
- Single (binocular) PD - one number, pupil to pupil. Example: 63.
- Dual (monocular) PD - two numbers, each pupil to the bridge of your nose. Example: 31 / 32.
Faces are rarely perfectly symmetric, so dual PD is more precise and is what careful labs prefer, especially for progressive lenses. PDgo gives you both automatically.
Distance PD vs near PD
When you look at something close, your eyes converge - so your near PD (for reading glasses) is about 3 mm smaller than your distance PD. Order forms usually want distance PD; reading-glasses forms may ask for near PD. PDgo shows a near-PD reference alongside your result.
Where do I find my PD?
- Your prescription - sometimes it's written there (look for "PD"), but many prescriptions omit it.
- Ask your optician - they measured it if you bought glasses there.
- Measure it yourself - with a free on-screen ruler or automatically in ~10 seconds with PDgo on any Face ID iPhone. See all three methods compared.