Frequently asked questions

Pupillary distance (PD), also called interpupillary distance (IPD), is the measurement in millimeters between the centers of your pupils. It's essential for properly positioning eyeglass lenses so the optical center aligns with your eyes, ensuring clear and comfortable vision.

When ordering glasses online, you need your PD to ensure the lenses are centered correctly. An incorrect PD can cause eye strain, headaches, and blurry vision. Many eye doctors don't include PD on prescriptions, so you may need to measure it yourself.

Single PD is the total distance between both pupils. Dual PD measures each eye separately from the center of your nose (e.g., Right: 31mm, Left: 32mm). Dual PD is more accurate since most people's faces are slightly asymmetrical.

Our precise measurement method using a reference card achieves accuracy within 1mm, comparable to professional optometry equipment. Unlike other online tools, we account for parallax and eye convergence for true precision. The free iris-based method is less accurate (±2-3mm). See our full accuracy comparison →

The free method uses your webcam to detect your iris and estimate PD. It's quick but less accurate. The premium method uses a standard-sized reference card (credit card, ID card) placed on your forehead for precise calibration, achieving professional-level accuracy.

For the free method, you just need a webcam or phone camera. For the premium method, you'll also need a standard-sized card (credit card, ID card, or library card) to use as a reference.

Premium access costs €1.99 for 24 hours. This gives you unlimited access to all premium tools including precise pupillary distance measurement and OC height measurement.

The premium features require significant development and maintenance to ensure professional-level accuracy. The one-time payment model ensures we can continue improving our tools without relying on ads or selling your data.

No. Since premium access is unlocked immediately upon purchase, no refunds can be provided. By completing your purchase, you expressly consent to immediate access and waive your right of withdrawal. Please try the free method first to ensure your device is compatible before purchasing.

No. All image processing happens entirely in your browser using local JavaScript. Your photos never leave your device and are never uploaded to any server. This is a core privacy guarantee of PupiMetric.

We only collect the minimum data necessary: your email address for account management and payment information processed securely by Stripe. We do not collect or store any photos or measurement data on our servers.

You can delete your account at any time from the Account Settings page. This will permanently remove all your data from our systems.