How to measure pupillary distance (PD)? A guide to PD measurement

What is PD (Pupillary Distance)?

Pupillary Distance (PD) is an important measurement for prescription glasses, representing the distance between the centers of your pupils, usually expressed in millimeters (mm).

When wearing glasses, the optical center of the lenses must align properly with your eyes; therefore, accurate PD data is an essential reference for eyewear.

If you already have your PD value on your prescription or eye exam report, you can provide it directly according to that data.

If you don't have your PD, don't worry—we have provided two common methods below to help you determine your pupillary distance.


How do I measure my PD?

When measuring your PD, it is most important to:

• Keep your head natural and upright
• Look straight ahead
• Keep the ruler level
• Do not squint or intentionally widen your eyes
• It is recommended to repeat the measurement several times

Everyone's PD is different; you cannot estimate it based on gender, age, or average values. Actual values should be based on personal measurement or professional eye exam results.


【Method 1】Measure your PD yourself with a ruler

A｜Measuring in front of a mirror

Tools needed:

A flat mirror and a ruler with clear millimeter (mm) markings.

Steps:

1. Stand upright in front of a mirror, keeping your head natural and upright, and look straight ahead. Avoid tilting your head up or down, or turning it side to side.

2. Hold the ruler level across the bridge of your nose, ensuring it remains straight and not bent.

3. Observe the millimeter mark that aligns with the center of one pupil and record the value.

4. Observe the millimeter mark that aligns with the center of the other pupil.

5. The distance between the centers of the two pupils is your PD.

Example:

Left pupil center: 31 mm
Right pupil center: 32 mm

PD ≈ 31 + 32 = 63 mm

If you can measure the monocular PD for each eye separately, you can record it as:

Right Eye PD: 32 mm
Left Eye PD: 31 mm


B｜Ask a friend to help you take a photo

If it is difficult to see clearly in the mirror, you can ask a friend to help take a photo.

Tools needed:

A smartphone or digital camera, and a millimeter ruler.

Method:

1. Place the ruler horizontally under your eyes or in an appropriate position.

2. Keep your head upright and look naturally straight ahead.

3. When taking a front-facing photo, keep the phone lens as parallel to your face as possible.

4. Compare the millimeter marks in the photo with the positions of your pupil centers.

5. Repeat the measurement a few times to confirm the results are consistent.

Tip:

If the phone is too close or the lens angle is tilted during the photo, image distortion may occur, so this measurement result should only be used as a reference.

【Method 2】Check existing prescription or eye exam data

If you have worn glasses before and have an old prescription or eye exam record on hand, you can check if your PD is already recorded.

Some prescriptions may record it separately as:

R/OD: Right eye
L/OS: Left eye

If your prescription includes monocular PD for each eye, you can provide that data directly.


What if I only have old glasses?

Old glasses can be used as a reference, but we do not recommend using the lens positions of old glasses as an exact PD value.

This is because the actual fit can be affected by factors such as:

• Nose pad position
• Frame size
• Pantoscopic tilt of the frame
• Frame slippage
• Fitting height

If you require precise eyewear data, we recommend having it re-measured by an optometrist.

⚠️ Please note when measuring PD

Self-measuring PD can be affected by factors such as head angle, the position of the ruler, mirror distance, and the determination of the pupil center, which may lead to measurement errors.

Recommendations:

① Measure 3–5 times consecutively

If the results are consistent each time, the measurement is relatively stable.

② Do not rely on a single measurement

If there is a large discrepancy between measurements, we recommend adjusting your posture and the position of the ruler before trying again.

③ Prioritize professional eye exam data

If your eye doctor's prescription or exam report already includes your PD, we recommend using that professional data.

④ Seek professional assistance for precision

For high prescriptions, special lenses, progressive lenses, or other lenses that require precise positioning, we recommend having a complete measurement performed by a professional.

What if I don't have a PD or eye prescription?

If you want to order glasses online but currently lack complete prescription data, first check if you have the following information:

SPH | Sphere
CYL | Cylinder (Astigmatism)
AXIS | Axis (Astigmatism axis)
PD | Pupillary Distance
ADD | Addition (if applicable)

If you are unsure what the numbers on your prescription mean, do not guess.

We recommend contacting your original eye clinic or optometrist to confirm your exam data before ordering.

Now that you have your PD, how do you choose glasses?

Once you know your PD, you can start picking a frame that suits you.

When choosing glasses, in addition to PD, you can also consider:

Frame width, lens size, bridge width, temple length, face shape, and your personal style.

MISSU21 offers a curated selection of optical glasses in various styles, including:

• TR90 flexible frames
• Metal frames
• Browline glasses
• Square frames
• Polygonal frames
• Oval frames
• Aviator frames
• Plastic-Aluminum frames

You can choose the perfect frame based on your face shape and daily style.


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Go to "OPTICAL" to view the full collection →

Need help with your order?

If you already have:

Eye prescription / Exam report / PD value

But you are unsure how to provide the information, please keep your data safe and contact MISSU21 for confirmation.

We will assist you in confirming the information needed for your order.


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