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How to Measure Pupillary Distance (PD)

Your Pupillary Distance (PD) is the distance in millimeters between the centers of your pupils. It’s a vital measurement that ensures your prescription lenses are properly aligned for clear, accurate vision.

At RX Safety, we’ve made it easy to get this measurement — whether you want a fast online tool or prefer to do it manually.

Fastest & Most Accurate: Use Our Online PD Tool – Luna

For a quick, easy, and accurate measurement, try Luna, our integrated online PD tool — available both before ordering and seamlessly during checkout at RX Safety.

Why Choose Luna?

  1. Accurate results in seconds
  2. Works on your phone or computer
  3. No measuring tools required
  4. Perfect for any prescription — single vision, bifocal, or progressive
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FOLLOW AUDIO/
video DIRECTIONS

Pay attention to the audio and video instructions provided. They will guide you through the process step by step.

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align your face &
hold a plastic card

Position your face and hold any plastic card against your forehead, following the on-screen image.

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your pd measurement
is ready!

After a few seconds, the resulting number is your pupillary distance.

What is PupilLARY Distance (or PD for Short)?

It is the distance in millimeters from the center of the pupil of the right eye to the center of the pupil of the left eye. To give you optimum vision, this measurement must be accurate so that the center of the lens is in line with the center of your eye.

Why Pupillary Distance Measurement Is Important: Your eyeglass lenses have an “optical center,” which is the ideal spot for your pupil to look through in order to have optimal vision. Having an accurate Pupil Distance measurement is the key to getting your lenses to line up with your pupils and provide the best possible results from your eyewear.

Single PD vs. Dual PD: Single PD, also known as “binocular PD,” measures the distance from the center of one pupil to the other.

On the other hand, Dual PD accounts for the distance between each pupil’s center and the bridge of the nose. In a dual PD measurement, two numbers are provided—the first for the right eye (OD) and the second for the left eye (OS). This configuration, often written as 31/30, is referred to as “monocular PD” and proves especially useful when selecting progressive lenses.

pupillary-distance

Pupil Distance Measurement: Typically measured by your optician or eye doctor during an eye exam using a pupillometer, this precise measurement may or may not be included in your prescription. While a pupillometer provides the most accurate Pupil Distance measurement, alternative reliable methods are available, as we’ll explore shortly.

How to Measure Pupil Distance:

If you’d rather take the measurement yourself, here are three easy ways to do it at home:

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1. Mirror Method (DIY)

What You’ll Need: A mirror and a millimeter ruler

  1. Stand about 8 inches from a mirror in good lighting.
  2. Close your right eye and align the 0 mm mark of the ruler with the center of your left pupil.
  3. Switch eyes — close your left eye and open your right — and note the measurement at the center of your right pupil.
  4. That number is your pupillary distance.

Tip: If lining up the pupils is difficult, you can measure from the outer edge of one iris to the inner edge of the other.

2. With a Friend’s Help

What You’ll Need: A friend and a millimeter ruler

  1. Focus on an object 10–20 feet away, keeping your head still and eyes steady.
  2. Ask your friend to line up the 0 mm mark of the ruler with the center of one pupil.
  3. Then have them measure across to the center of the other pupil.
  4. Record that number — that’s your PD.

Note: This method tends to be more accurate than doing it solo.

4. Marking Method (Using Glasses)

What You’ll Need: Glasses, a non-permanent marker, and a millimeter ruler

  1. Put on your glasses and focus on an object 20 feet away.
  2. Carefully mark a dot on each lens over the object — one for each eye.
  3. Remove your glasses and measure the distance between the two dots.
  4. The result in millimeters is your PD.

Reminder: Clean the marks off your lenses right after measuring.

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Need Help or Have Questions?

If you’re unsure which method is right for you, or you’d like help reading your results, the team at RX Safety is happy to assist. Don’t let PD measurement slow down your order — whether you go high-tech with Luna or take the DIY route, we’ve got you covered.

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Frame’s
Measurements

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Segment Height

How to measure the segment height

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At RX Safety, our commitment to precision extends to default settings, ensuring tailored eyewear even without a specific Pupil Distance measurement. This process is not just about measurement—it’s about crafting eyeglasses that harmonize with individual needs, prioritizing clarity and comfort.

Measuring-Your-PD-Also-Known-as- Pupil-Distance

HOW TO Measure Your PD
or better know as Pupil Distance

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