How to Measure Your Pupillary Distance (PD) at Home

Your pupillary distance (PD) is the gap between the centres of your two pupils, measured in millimetres. Opticians use it to centre each lens over your eyes. If you're ordering glasses online, you'll usually need to supply it yourself — and the good news is that learning how to measure pupillary distance at home takes about two minutes. This guide walks through three reliable methods so you can measure PD without an optician, for free.

What you'll need

• A credit or ID card. Any standard card is exactly 85.60 mm wide (the ISO/IEC 7810 ID-1 size). Because that width never changes, it works as a perfect scale reference to convert pixels into millimetres.
• Good, even lighting. Face a window or lamp so your pupils are easy to see and there are no harsh shadows across your face.
• A mirror — only needed for the offline printable-ruler method below.

Method 1: Webcam method (most accurate)

The fastest way to measure your PD at home is to let your webcam do the work. Open the free PD tool and follow these steps:

1. Hold a standard credit or ID card flat against your forehead, or just under your eyes, so its long edge is level.
2. Face the camera straight on in good lighting and keep your head upright — no tilting left, right, forward, or back.
3. Let the tool detect your pupil centres and the card edges automatically. It uses the card's known 85.60 mm width to turn the on-screen distance into real millimetres.
4. Read your PD, then take a second reading and use the average. Write the number down for your glasses order.

Everything happens in your browser. There's no upload, no account, and no sign-up — your camera feed and photo never leave your device.

Method 2: Photo upload method

No working webcam? You can measure pupillary distance online for free from a selfie instead:

1. Take a straight-on selfie while holding a credit or ID card under your eyes, with the card edge level and fully in frame.
2. Make sure both pupils and the whole card are sharp and well lit.
3. Load the photo into the tool. It reads the card as the scale reference and measures the distance between your pupils.
4. Confirm the result with a second photo if you want extra confidence.

Even though it's called "photo upload," the image is processed locally in your browser. Nothing is sent to a server.

Method 3: Printable ruler + mirror method

If you'd rather work offline, you can do this the classic way with a millimetre ruler and a mirror:

1. Print the printable PD ruler at 100% scale (no "fit to page") and check its length against a real ruler.
2. Stand about 20 cm from a mirror and rest the ruler flat against your brow.
3. Close your right eye and line the ruler's zero mark up with the centre of your left pupil.
4. Without moving the ruler, open your right eye and close your left, then read the millimetre mark over your right pupil. That number is your PD.

Tips for accuracy

• Keep your head level and look straight ahead, not down at the camera.
• Hold the card flat against your skin — a tilted or angled card throws off the scale.
• Take two or three readings and average them.
• For glasses you'll wear at a desk or for reading, see near PD for reading glasses, which is slightly smaller than your distance PD.
• If your optician gave you two numbers, read dual and monocular PD to understand what each one means.

How accurate is it?

Under good conditions — even lighting, a level card, and a straight-on pose — these methods land within about ±1–2 mm, which is well inside the tolerance most lens labs work to. That said, this is a measurement aid, not a medical device. For high-prescription, progressive, or specialty lenses, it's worth confirming the figure with an eye-care professional. To understand what the number means and why it matters, read what is pupillary distance.

How to measure PD — frequently asked questions

How do I measure my PD at home?

Hold a standard credit card flat against your forehead as a size reference, look straight into your webcam or take a front-facing photo, and let the tool detect your pupils and the card to convert the distance to millimetres. It takes about a minute and needs no optician.

Can I measure my pupillary distance without an optician?

Yes. With a webcam or a single selfie and a standard card for scale, you can measure your PD accurately at home for free. Take two readings and average them to confirm the result.

How do I measure PD without a ruler?

Use the webcam or photo method: a standard 85.60 mm card provides the scale instead of a ruler, and the tool calculates your PD from the image. If you prefer a ruler, print our true-to-scale PD ruler and read it in a mirror.

What is a normal PD for adults?

Most adults have a PD between about 54 and 74 mm, with an average near 63 mm — roughly 61 mm for women and 64 mm for men. Children have smaller values.

How accurate is measuring PD at home?

With good lighting, a level card and a straight-on pose, home PD measurement is typically accurate to within about ±1–2 mm — fine for standard single-vision glasses. Confirm strong or progressive prescriptions with an optician.

How do I get my PD for ordering glasses online?

Measure it with your webcam, a photo, or a printable ruler, note the total PD in millimetres (and dual or near PD if the retailer asks), and enter it in the PD field at checkout.