How to Measure Your Pupillary Distance (PD)
Pupillary distance (PD) is the space between the centers of your pupils, measured in millimeters. An accurate PD ensures the optical center of each lens lines up properly for clear, comfortable vision.
WHAT IS PUPILLARY DISTANCE?
Pupillary Distance (PD) measures the spacing between your pupils. Eyeglass lenses are manufactured so their optical centers match this measurement, which is what allows your eyes to focus naturally and comfortably through the lenses.
BEFORE YOU BEGIN
- Stand in bright, even lighting facing a mirror at eye level.
- Keep your head straight and focus on a distant object.
- Use a millimeter ruler or printable PD ruler.
- Move hair or accessories that might shift the ruler.
- Take several readings and use the most consistent result.
WHY PD IS IMPORTANT
When PD is correct, your eyes look directly through each lens’s optical center. If the measurement is off, you may experience:
- Eye fatigue or strain
- Blurred or distorted vision
- Frequent headaches, especially with screen use
- Discomfort during reading or close work
Measure Your PD Yourself (Mirror Method)
Tools needed: millimeter ruler and mirror. Repeat several times for accuracy.
- Stand roughly 8 inches (20 cm) from a mirror.
- Place the ruler flat against your brow.
- Close your right eye and align 0 mm with the center of your left pupil.
- Keeping the ruler still, switch eyes.
- Note the measurement at the center of your right pupil. That value is your PD.
Tip: Look straight ahead and keep your head level during measurement.
Have Someone Measure (Most Precise)
- Look at a target 10–20 ft (3–6 m) away with both eyes open.
- Your helper aligns the ruler’s 0 mm with one pupil.
- They measure straight across to the center of the other pupil.
- Have them position slightly below your eye level.
- Keep your gaze fixed on the distant target.
- Repeat and record the most consistent reading.
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