How to Measure Pupillary Distance at Home — 3 Easy Methods
Pupillary Distance (PD) is the measurement in millimeters between the centers of your pupils. It is required for ordering prescription glasses online — without it, your lenses will not be centered correctly, causing eye strain and blurry vision. Yet many optometrists conveniently forget to include PD on your prescription. Here are three ways to measure it yourself.
Method 1: The Ruler Method (Most Accurate)
- Stand in front of a mirror in good lighting
- Hold a millimeter ruler across your eyebrows
- Close your right eye. Align the 0mm mark with the center of your left pupil
- Close your left eye, open your right. Read the measurement at the center of your right pupil
- Repeat 3 times and take the average
Typical PD for adults: 54-68mm for women, 56-72mm for men.
Method 2: The Credit Card Method
If you do not have a millimeter ruler, use a standard credit card (85.6mm wide). Take a selfie looking straight at the camera while holding the card just below your eyes. Measure the distance between your pupils relative to the card width in any photo editing software. Formula: PD = (pupil distance in pixels / card width in pixels) × 85.6.
Method 3: Online PD Tools
Several online glasses retailers offer free webcam-based PD measurement tools. Zenni Optical and EyeBuyDirect both have them — you hold a standard card to your forehead, and the tool uses your camera to calculate PD automatically. Accuracy is within 1-2mm, which is adequate for most prescriptions.
Single PD vs Dual PD
Some online stores ask for dual PD (left eye and right eye separately). If you only have single PD, divide by 2 to estimate each eye — but for high prescriptions (above ±4.00), ask your optometrist for the dual measurement.