Pupillary Distance (PD)
This measurement is for patients of the practice. Enter the access code your office gave you when your visit was arranged, then tap Continue.
If you don't have a code, please contact the office and we will be glad to provide one.
This is a measurement aid, not a diagnosis and not a prescription. A PD measured in the office remains the definitive value for complex prescriptions.
Before you begin
Your pupillary distance (PD) is the distance, in millimeters, between the centers of your two pupils. Glasses lenses are centered on this number, so it has to be right. Most adults measure between 54 and 74 mm. This tool measures it three times and checks that the three agree — that agreement is what makes the number trustworthy.
How it works
- You will need a standard bank card / credit card. Every bank card is exactly 85.6 mm wide — the tool uses it as the ruler in your photo.
- Hold the card flat against your forehead, long edge horizontal, just above your eyebrows, and take a photo looking straight into the camera, eyes looking far away — not at the screen up close.
- On the photo, you drag small markers onto the two edges of the card and the centers of your two pupils. A magnifier helps you place them exactly.
- You repeat this three times, with a fresh photo each time. The tool takes the middle value and reports how closely the three agreed.
- Take your glasses off for the photo. Sit in good, even light, facing the camera squarely — a turned or tilted head is the main source of error.
Choose a method
If the camera is unavailable or you would rather not use it, the mirror method works — it is simply easier to get slightly different readings, and the report will say which method was used.
Used only on your report, so the office can match it to your chart.
About this measurement
A single quick PD measurement — including most one-shot online tools — can be off by several millimeters, and a lens centered even 2 mm off can strain your eyes. That is why this tool insists on three independent measurements and reports their agreement, and why a set of readings that disagree too much is labeled UNRELIABLE instead of averaged into a false sense of precision. For high prescriptions, progressives, and prism, the office measurement remains definitive.
Glasses off. Card flat against your forehead, long edge level. Face the camera squarely, look past the camera into the distance, and keep your head still.
Drag each marker to its exact spot. The green markers go on the left and right edges of the card; the red markers go on the centers of your pupils; the amber marker goes on the center of your nose bridge, between your eyes. A magnifier follows your finger or mouse.
This photo stays on your device. It is used only to place the markers, it is never sent to the office, and it is discarded when you leave this page. Only the numbers go on your report.
Mirror & ruler
Stand about 8 inches (20 cm) from a mirror, in good light, glasses off. You will take the reading three times, resting your eyes in between.
How to read it
- Hold a millimeter ruler flat against your brow, level, numbers facing the mirror.
- Close your right eye. With your left eye, line the ruler's 0 up with the center of your left pupil as you see it in the mirror.
- Without moving the ruler, close your left eye and open the right. Read the mark at the center of your right pupil. That number is one PD reading.
- Look away, rest a moment, and repeat from the beginning — three readings in all. Type each one in below, exactly as read, fractions included (for example 63.5).
Your result
Your PD report is below.
Pupillary Distance (PD) Report — Paddy Kalish OD, 1296 Beacon St, Brookline, MA 02446
| Ordered by | Paddy Kalish, OD |
|---|---|
| Attempted by | |
| Report status | |
| Method |
How to read this: your distance PD is the number used for regular glasses. The monocular PDs give each eye's share — the right and left need not be equal, and order forms that ask for two numbers want these. Near PD (for reading glasses) is about 3 mm less, because your eyes turn slightly inward up close; the figure here is that standard estimate, not a separate measurement. The agreement line is the spread between your three measurements — 1 mm or less is excellent, up to 2 mm is acceptable, and more than that means the readings cannot be trusted as one number.
Your report
Your report was prepared automatically when the measurement ended — there is nothing to approve or send. Download another copy as a PDF below if you would like one for your own records.
Measurement aid only — not a diagnosis and not a prescription. Accuracy depends on a level card, a square-on photo, and careful marker placement. For high prescriptions, progressives, or prism, and whenever this result and an office measurement disagree, the office measurement governs.