Understanding Pupillary Distance (PD)
Posted by Svitlana Koren on

Understanding Pupillary Distance (PD)

Pupillary distance, commonly abbreviated as PD, is the measurement in millimeters between the centers of the pupils of your eyes. This measurement is crucial for ensuring that the lenses of your glasses correctly align with your pupils, providing optimal vision clarity.

If your eye care professional hasn't provided this measurement on your prescription, you can easily measure your PD at home. To do so, download and print our PD ruler and follow the instructions provided.

Measuring Pupillary Distance

Using a PD Ruler

To measure someone else's PD (or have yours measured by a friend), use our PD ruler. Begin by folding the ruler and selecting the side labeled "Using a friend." The person being measured should sit and fix their gaze on an object about 10 to 20 feet away to stabilize their gaze.

Position the PD ruler on the forehead, aligning the zero mark with the center of the right pupil. The measurement above the left pupil's center indicates the PD. For accuracy, you might find it helpful to close one eye to focus on reading the numbers.

Measuring Your Own PD

You can measure your PD alone with the help of a mirror and our PD ruler. Here's how:

  1. Fold the ruler and use the side marked "Using a mirror."
  2. Stand roughly 8 inches from a mirror. Place the ruler horizontally across your eyes, aligning zero directly over your left pupil. For stability, you may hold the ruler against your forehead.
  3. Close or cover your left eye. The number directly above your right pupil is your PD.

Repeat this measurement a few times to ensure accuracy, averaging your results if they vary.

Understanding Your Prescription

For those needing progressive or bifocal lenses, measuring the near focus PD is essential. This requires another person's help to ensure accuracy, focusing on a pen held between you and the measurer instead of a distant object.

Identifying Your PD on a Prescription

Your PD ensures that your lenses are perfectly positioned over your pupils, particularly vital for those with high-powered lenses. It may appear as a single number (e.g., 64 mm) or as two numbers (e.g., 32 and 31 mm for each eye) on your prescription.

Average PD Measurements

The average PD ranges from 48 mm to 73 mm, with women typically around 60 mm and men about 64 mm. These figures can vary widely among individuals.

Single vs. Dual PD

A single PD is the total distance between the pupils, while a dual PD represents the distances from each pupil to the bridge of the nose. Dual PD is usually noted with two numbers, indicating the measurement for each eye starting with the right.