This free PD ruler online measures your pupillary distance (PD), the distance in millimeters between the centers of your pupils. You need it to order glasses online. Use your webcam with the tool below, or print an actual size PD ruler and measure with a mirror. Both take about a minute.
Estimate your PD directly in your browser. All image processing stays 100% on your device — nothing is uploaded to any server.
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Hold any standard bank card (85.60 mm) flat against your forehead just above your eyebrows, look straight into the camera, and take a photo.
No webcam? Use the Printable PD Ruler section or the mirror method below.
Pupillary distance, also called interpupillary distance (IPD), is the distance between the centers of your two pupils, measured in millimeters. Opticians use it to place the optical center of each lens directly in front of your pupil. If the lenses sit off-center, you can get blurred vision, eye strain or headaches, and the problem grows with stronger prescriptions.
Your PD is not usually printed on a standard prescription, so when you order glasses online you often need to measure it yourself. Online glasses stores, including Zenni and Zeelool, ask for a PD when you order.
| Type | What it measures | When you need it |
|---|---|---|
| Binocular (single) PD | Pupil to pupil, one number (for example 63 mm) | Most single-vision glasses |
| Monocular (dual) PD | Nose bridge to each pupil: right (OD) and left (OS), two numbers (for example 31.5 / 31.5) | Progressive and bifocal lenses, strong prescriptions, uneven face |
| Distance PD | PD while looking at something far away | Distance and everyday glasses |
| Near PD | PD while looking at something close, usually around 3 mm less than distance PD | Reading glasses |
Your two monocular numbers add up to your binocular PD. If your right pupil is 31 mm from the center of your nose and your left is 32 mm, your PD is 63 mm.
| Group | Typical PD range |
|---|---|
| Adults | 54 to 74 mm, with an average of about 63 mm |
| Children | 43 to 54 mm |
If your measurement falls far outside these ranges, measure again. A typical mistake is reading from the edge of the pupil instead of its center.
You can measure PD with any millimeter ruler: a physical one, or a printed one that you have checked for true size.
That number in millimeters is your PD. Repeat a few times and average.
Ask a friend to hold the ruler against your brow while they stand about 20 to 30 cm (8 to 12 inches) in front of you. Look at their nose bridge, not at the ruler. They line up 0 with one pupil and read the other.
A bank card is exactly 85.60 mm wide (ISO/IEC 7810 ID-1), so it works as a scale:
Use this formula:
For example, if the card is 900 px wide and your pupils are 640 px apart, your PD is 640 ÷ 900 × 85.60 ≈ 60.9 mm.
A printable PD ruler lets you use the mirror or friend method without a physical ruler. Use the printable paper ruler on our homepage and print it at true size:
A printed ruler that is even 2% too small makes your PD about 1 mm too small, so always do the card check.
An online or home measurement is an estimate. With careful setup it is usually close enough for low-power, single-vision glasses, but a small error matters more when your prescription is strong or when you order progressive or bifocal lenses. For those, ask an optician for your monocular PD and fitting heights.
This tool is not a medical device and does not replace an eye exam or an optician's measurement. If your glasses feel wrong after you receive them, see an optician.
Hold a millimeter ruler against your brow in front of a mirror. Close your right eye and line up 0 with your left pupil, then open your right eye, close your left, and read the mark at the center of your right pupil. That number is your PD in millimeters.
A PD ruler is a ruler with millimeter markings used to measure the distance between your pupils. You can use a printable one or an online PD ruler like this page.
It gives a good estimate when you measure carefully and repeat the reading, but it is not as exact as an optician's pupillometer. Use it for simple single-vision glasses and ask an optician for stronger or progressive prescriptions.
Most adults have a PD between 54 and 74 mm, with an average of about 63 mm. Children typically measure 43 to 54 mm.
Single (binocular) PD is one number from pupil to pupil. Dual (monocular) PD is two numbers: the distance from your nose bridge to each pupil. Dual PD is more accurate when your face is not perfectly symmetrical.
Near PD is the distance between your pupils when you look at something close, such as a book. It is usually about 3 mm less than your distance PD and is used for reading glasses.
Yes. Online glasses stores ask for your PD in millimeters, and you can enter the number you measure here. Check each store's instructions for single or dual PD fields.
Yes. Print the paper ruler on our homepage at 100% scale, check it against a credit card (85.60 mm wide), and use it with the mirror method above.
Children usually have a PD of 43 to 54 mm. A child moves a lot, so the photo or friend method with a helper works best. For children's glasses, ask an optician.
The online tool uses your webcam. Without one, use a printable PD ruler or a physical millimeter ruler with the mirror method.