PD Measurement Online — Free & Instant

Why Measure Your PD Online?

Online glasses retailers — from Zenni to Warby Parker — require your PD before they can make your prescription lenses. Getting this number used to mean booking an appointment, but now it takes less than 30 seconds from your phone.

How Our Online PD Tool Works

We use face-api.js, an AI face landmark detection library that runs entirely in your browser. It maps 68 points on your face and calculates the pixel distance between your pupil centres, then scales that to millimetres using average facial proportions.

Because all processing happens on your device, your photo is never uploaded anywhere. This makes our tool both faster and more private than cloud-based alternatives.

Tips for an Accurate Online PD Measurement

• Face the camera straight-on — no tilting or turning
• Use even, natural lighting (avoid harsh shadows)
• Keep your eyes wide open and look directly at the lens
• Remove glasses or sunglasses before measuring
• Hold your phone at arm's length for the best angle

Is Online PD Measurement Accurate Enough?

For most prescription strengths (up to ±4 diopters), an online PD measurement within ±2mm is perfectly adequate for ordering glasses. For high-power prescriptions or progressive lenses, a professional measurement is recommended as well.