To measure your pupillary distance (PD), which is the distance between the centers of your pupils in millimeters, follow these steps:

What You Need

• A millimeter ruler (or a printable PD ruler)
• A mirror or a friend to help
• A well-lit area

Step-by-Step Measurement

1. Positioning
Stand about 8 to 20 inches (20 to 50 cm) away from a mirror or sit facing a friend. Keep your head straight and look directly ahead at a distant point to keep your eyes steady

. 2. Using a Ruler

• Place the ruler horizontally against your brow or nose bridge.
• Align the 0 mm mark with the center of one pupil (usually the right eye).
• Without moving your eyes, read the millimeter marking that lines up with the center of your other pupil (left eye). This number is your single PD measurement

3. Measuring Monocular (Dual) PD (Optional)

• For more precision, measure the distance from the center of your nose to each pupil separately.
• Place the 0 mm mark at the center of your nose and measure to the center of each pupil.
• This gives you two numbers (e.g., 32/30 mm), which is useful for certain prescriptions

4. Repeat for Accuracy
Measure a few times to ensure consistency, then average the results if needed

Additional Tips

• If measuring near PD (for reading glasses), focus on an object about 40 cm away instead of a distant point, and have someone else help measure

• Keep your eyes still and do not look at the ruler while measuring

• If you have difficulty, many online tools and apps can assist with camera-based PD measurement

Knowing your PD is important to ensure your lenses are correctly centered, avoiding eye strain and ensuring clear vision

. In summary, measuring PD involves using a ruler to measure the distance between your pupils while looking straight ahead, either by yourself using a mirror or with the help of another person. Monocular PD measurements can provide more accuracy if needed.