Pupillary Distance (PD) Tool

Pupillary distance (PD) is the distance between the centers of the pupils, usually recorded in millimeters. Optical labs use PD to place the optical centers of lenses appropriately for the wearer’s eyes.

This tool explains single PD, dual (monocular) PD, and distance versus near PD concepts. Home measurements can be imprecise; many prescriptions include PD, and opticians can measure it professionally.

Follow these educational steps:

1. Read the on-screen definitions for single, dual, distance, and near PD.
2. If you practice a selfie-ruler method, follow the alignment tips carefully and repeat measurements.
3. Compare your notes with any PD printed on a glasses prescription or order form.
4. Prefer professional measurement for progressive lenses or higher prescriptions.
5. Never invent a PD to bypass optical safety checks when ordering medical devices.

A PD value is a fitting measurement, not a diagnosis. Dual PD values (right and left) can differ slightly. Near PD is typically a bit smaller than distance PD because the eyes converge for close work.

If your numbers vary widely between attempts, that variability itself is a reason to get a professional measurement rather than average random guesses.

This tool does not guarantee lens centration accuracy for online orders.

It does not replace an optician’s pupillometer or digital centration process.

Important limitations:

• Camera parallax and ruler tilt create errors.
• Children and people who struggle to fixate need in-person measurement.
• Progressive lenses are less forgiving of PD mistakes than simple single-vision readers in many cases.

Ask your eye-care professional or optician for PD if it is missing and you need new glasses. Seek care for eye-alignment concerns (eye turn, double vision) rather than trying to fix them with PD guesses.