How to Measure Pupillary Distance (PD)

When ordering prescription glasses, one key number ensures clear, comfortable vision: your Pupillary Distance (PD). Eye doctors usually include your PD on your prescription, but if it's missing, no worries. This article explains what PD is, why it's so important, and guides you step-by-step on how to measure it accurately.

What is PD?

Pupillary Distance (PD) is the distance between the centers of your two pupils, measured in millimeters (mm). Think of it as the exact point where you naturally focus your eyes. Getting this measurement right ensures that the optical center of each lens aligns perfectly with your eyes — giving you the clearest, most comfortable vision possible.

Why is PD important?

A correct PD helps your glasses:

Align the lenses properly with your eyes
Reduce eye strain, headaches, and blurry vision
Maximize the effectiveness of your prescription
Improve comfort for long hours of wear

Even the most accurate prescription won't perform well if your PD is off.

Understanding Single and Dual PD

Single PD is one measurement (e.g., 62 mm) representing the total distance between your pupils. This is suitable for most eyeglasses, especially if your face is symmetrical.
Dual PD uses two numbers (e.g., 32/34 mm) measuring the distance from your nose bridge to each pupil. It's ideal for asymmetrical faces or complex prescriptions, providing a more tailored fit. Both Single and Dual PD have Distance and Near variations for different vision needs.
Common PD Ranges
- Women: 53-72mm (average around 63mm)
- Men: 55-74mm (average around 65mm)

Remember that your PD is unique to you, and even small deviations from your correct measurement can impact your visual comfort.

How to Measure Your PD

Option 1: Check Your Existing Prescription

Your optometrist may have included your PD on your prescription. Look for:

PD 63" (single PD) → total distance between pupils
PD 31/32" (dual PD) → distance from each eye to the center of your nose

Option 2: Measure It Yourself at Home

You’ll need:

A millimeter ruler
A mirror

Steps:

1. Stand about 8 inches (20 cm) from a mirror.

2. Hold the ruler against your brow, resting it above your eyes.

3. Close your right eye and align the 0 mm mark with the center of your left pupil.

4. Without moving the ruler, close your left eye and open your right eye.

5. Read the measurement at the center of your right pupil — that's your PD!

Tip: Take the measurement 2-3 times to ensure accuracy. For best results, have someone take a photo of you holding the ruler and measure from the photo.

Option 3: Get Help from a Friend

You’ll need:

A millimeter ruler
A friend to help

Steps:

Sit facing your friend at eye level in a well-lit area.
Look straight ahead at a distant object.
Have your friend hold the ruler across your brow.
Your friend should measure the distance between the centers of your pupils.
Take multiple measurements for accuracy.

For the most accurate results, especially for progressive or high-index lenses, consider professional measurement:

Optometrist or Ophthalmologist: They use specialized equipment called a pupillometer for precise measurements.
Optical Shops: Most eyewear retailers offer PD measurement services, sometimes complimentary with an eyeglass purchase. Advanced optical shops use digital devices that can measure not only PD but also other important fitting parameters.

Frequently Asked Questions

Q: What if my measurements vary slightly each time?

A: This is normal. Take the average of 3-5 measurements for the most accurate result.

Q: Does my PD change over time?

A: Adult PD generally remains stable. Children's PD increases as they grow until early adulthood.

Q: Is PD different for reading glasses vs. distance glasses?

A: Yes. Near PD (for reading) is typically 2-3mm less than distance PD because your eyes converge when looking at close objects.

Q: How precise does my PD need to be?

A: For standard single-vision lenses, being within 1-2mm is usually acceptable. For high-prescription or progressive lenses, precision within 0.5mm is ideal.