What Is PD on a Glasses Prescription? How to Find Your Pupillary Distance

If you have ever ordered prescription glasses online, you may have been asked to enter a number called PD.

But what does PD mean on a glasses prescription? Where can you find it, and what should you do if your prescription does not list it?

PD stands for pupillary distance. It is the measurement between the centers of your pupils, expressed in millimeters. This measurement is used when positioning prescription lenses in front of your eyes. (Cleveland Clinic)

This guide explains what PD means, the difference between single and dual PD, how PD is measured, and what to consider before ordering prescription glasses online.

Important: This guide is for understanding and measuring an existing PD. It does not replace an eye examination or professional eye-care advice.

What Does PD Mean on a Glasses Prescription?

PD, or pupillary distance, is the distance between the centers of your pupils. It is measured in millimeters (mm) and is used when making prescription eyeglasses. (Cleveland Clinic)

For example, a prescription may list:

PD: 63 mm

This means the measured distance between the centers of the two pupils is 63 millimeters.

PD is different from SPH, CYL, AXIS or ADD. Those values describe different aspects of a lens prescription, while PD is a measurement used for positioning the lenses.

For a complete explanation of prescription abbreviations, read our How to Read a Glasses Prescription guide.

Is PD Part of a Glasses Prescription?

PD is commonly used when preparing prescription eyewear, but it may not appear on every printed prescription.

The American Optometric Association notes that the FTC's current Eyeglass Rule does not require pupillary distance to be included on the prescription itself. (American Optometric Association)

This means you may receive a valid glasses prescription that lists values such as SPH, CYL and AXIS without a PD measurement.

If your PD is not listed, you can ask your eye-care professional for the measurement or follow the measurement instructions provided by your eyewear provider.

What Is a Single PD?

A single PD, also called binocular PD, is one measurement representing the distance between the centers of both pupils.

For example:

PD: 63 mm

This is one number for both eyes.

Single PD is the most common format described for pupillary distance. (Cleveland Clinic)

What Is a Dual PD?

A dual PD, also called monocular PD, provides two separate measurements.

One measurement represents the distance from the center of the nose to the center of the right pupil, and the other represents the corresponding measurement for the left pupil.

For example:

PD: 31/32 mm

The first number generally represents the right eye and the second number the left eye. (Cleveland Clinic)

A dual PD can provide more individual measurements for each eye than a single binocular PD.

What Is the Difference Between Single PD and Dual PD?

PD Type	What It Measures	Example
Single PD	Distance between the centers of both pupils	63 mm
Dual PD	Separate measurement for each eye	31/32 mm

Neither format should be changed or converted simply because an online ordering form uses a different format.

Use the measurement provided by your eye-care professional or follow the exact instructions supplied by your eyewear provider.

How Do You Find Your PD?

There are several ways to obtain a PD measurement.

Option 1: Ask Your Eye-Care Professional

The most straightforward option is to ask for your PD when you receive or update your glasses prescription.

Cleveland Clinic notes that an eye-care specialist can measure PD using professional tools and that professional measurement is the most accurate option. (Cleveland Clinic)

This can be particularly useful when you need specialized lens designs, such as progressive lenses.

Option 2: Measure Your PD at Home

It is possible to measure PD at home using a millimeter ruler and a mirror.

However, home measurements can vary in accuracy. Cleveland Clinic recommends professional measurement when greater precision is important, including for people who need progressive or other specialized lenses. (Cleveland Clinic)

How to Measure PD With a Mirror

If you choose to measure your PD at home, use a well-lit room and a ruler with millimeter markings.

Step 1: Stand in Front of a Mirror

Stand approximately 18 inches, or 46 centimeters, from the mirror.

Keep your head straight and look directly at the mirror.

Step 2: Position the Ruler

Hold the ruler horizontally underneath your eyes so that the millimeter markings are visible in the mirror.

Keep the ruler steady.

Step 3: Align the Zero Mark

Close your left eye.

Using your right eye, align the zero mark on the ruler with the center of your right pupil.

Step 4: Measure the Other Pupil

Open your left eye and close your right eye without moving the ruler.

Look at the center of your left pupil and record the millimeter mark that aligns with it.

The measurement you obtain represents your approximate PD.

Cleveland Clinic provides a similar home-measurement method using a ruler and mirror. (Cleveland Clinic)

Is It Easier to Measure PD With Someone's Help?

Usually, yes.

Having another person hold the ruler can make it easier to keep the ruler level and reduce movement while you look straight ahead.

Cleveland Clinic also describes a method in which another person takes the measurement while you maintain a fixed head position. (Cleveland Clinic)

Whether measuring alone or with help, the goal is to obtain a consistent measurement rather than repeatedly adjusting the ruler.

Can I Use a Smartphone App to Measure PD?

Some smartphone applications can estimate PD, but the accuracy can vary between methods and devices.

Cleveland Clinic notes that smartphone apps can be used to help measure PD, while also emphasizing that professional measurement provides the most accurate reading. (Cleveland Clinic)

For everyday eyewear, an app may be a convenient reference, but you should follow your eyewear provider's requirements for the specific product you are ordering.

Does PD Change?

PD generally changes as a person's eyes grow during childhood. In adults, it usually remains relatively stable. (Cleveland Clinic)

However, different viewing tasks can sometimes involve slightly different measurements.

This is one reason accuracy can matter when choosing certain lens designs.

Does PD Need to Be the Same for Both Eyes?

No.

A single PD uses one measurement for both eyes, while a dual PD provides a separate measurement for each eye.

If your prescription or measurement includes separate right-eye and left-eye values, enter them according to the format provided.

Do not average, swap or convert the numbers unless your eyewear provider specifically instructs you to do so.

Is PD the Same as Frame Size?

No.

PD and frame measurements describe different things.

PD refers to the distance between the pupils or the individual pupil-to-nose measurements used for lens positioning.

Frame measurements describe the dimensions of the eyewear, such as lens width, bridge width and temple length.

A frame can have an appropriate overall size while still requiring an appropriate PD measurement for prescription lens positioning.

Is PD the Same as Bridge Width?

No.

This distinction is especially important when choosing frames online.

PD measures the position of your pupils.

Bridge width is a measurement of the frame itself.

The two measurements are related to different parts of the eyewear-fitting process.

If you are trying to understand how bridge design affects frame fit, read our guide to High Bridge vs. Low Bridge Glasses.

Why Does PD Matter When Ordering Glasses Online?

PD is used when positioning prescription lenses in front of the eyes.

Cleveland Clinic explains that eye-care professionals use PD when making prescription eyeglasses so the lenses can be positioned appropriately relative to the eyes. (Cleveland Clinic)

For online orders, this means you should provide the PD measurement requested by the specific eyewear provider and enter it exactly as instructed.

PD is only one part of the information required for prescription eyewear.

Depending on the product, you may also need:

• OD and OS

• SPH

• CYL

• AXIS

• ADD

• PD

Not every prescription contains every value.

What Should I Do If My Prescription Does Not Include PD?

First, check whether your prescription document lists PD elsewhere.

If it does not, you can:

Ask your eye-care professional for your PD measurement.

Ask your eyewear provider whether a specific PD format is required.

Use an approved measurement method provided by the eyewear provider.

Avoid guessing a PD value when you can obtain a reliable measurement.

This is particularly important when ordering specialized lens designs such as progressive lenses.

Is PD Different for Progressive Lenses?

Progressive lenses have multiple viewing zones within one lens, so accurate measurements and fitting information are especially important.

Cleveland Clinic specifically recommends professional PD measurement for people who need special lenses such as bifocals, trifocals or progressive lenses. (Cleveland Clinic)

If your prescription includes an ADD value and you are considering progressive lenses, use the prescription information provided by your eye-care professional rather than trying to calculate or modify the values yourself.

You can learn more about ADD and progressive lenses in our glasses prescription guide.

Can I Use My Old PD Measurement?

It depends on the situation.

For adults, PD is generally stable, but measurements can vary depending on the method used and whether the measurement is binocular or monocular.

If you already have a recent and reliable PD measurement and your eyewear provider accepts that format, you may be able to use it.

When in doubt, ask your eye-care professional or eyewear provider whether an updated measurement is recommended.

Can PD Be Used to Calculate My Prescription?

No.

PD is a measurement used for eyewear fitting and lens positioning. It does not replace the optical values on your prescription.

For example, PD does not tell you your:

• SPH

• CYL

• AXIS

• ADD

Those values should come from your existing prescription issued by a qualified eye-care professional.

For a complete explanation, see How to Read a Glasses Prescription: SPH, CYL, AXIS & ADD Explained.

What Information Do I Need to Order Prescription Glasses Online?

The exact information depends on the product and the eyewear provider.

You may need:

Prescription information:
SPH, CYL, AXIS, ADD and other values listed on your prescription.

Eye designation:
OD and OS identify the right and left eyes.

PD:
Single or dual PD, depending on the ordering system.

Frame information:
The selected frame and its available lens options.

Before placing an order, make sure the information you provide matches your existing prescription.

For customers using PHANEO's prescription lens options, provide or upload the prescription information requested during the ordering process.

Frequently Asked Questions

What does PD stand for on a glasses prescription?

PD stands for pupillary distance. It is the measurement between the centers of the pupils, expressed in millimeters, and is used when making prescription eyeglasses. (Cleveland Clinic)

What is a normal PD for adults?

Adult PD values vary from person to person. Cleveland Clinic describes an average adult PD of around 63 mm, with a typical range of approximately 50–70 mm. (Cleveland Clinic)

An individual prescription should use the person's actual measurement rather than an average value.

Is 63 mm a common PD?

63 mm is around the average adult PD reported by Cleveland Clinic, but individual measurements vary. Do not use 63 mm simply because it is a commonly cited average. (Cleveland Clinic)

What does dual PD mean?

Dual PD provides two measurements, generally representing the distance from the center of the nose to the center of each pupil. For example, a dual PD could be written as 31/32 mm. (Cleveland Clinic)

Is PD required on an eyeglass prescription?

Not necessarily. The American Optometric Association notes that the FTC's Eyeglass Rule does not require PD to be included on the prescription itself. (American Optometric Association)

However, PD may still be required by an eyewear provider when ordering prescription glasses.

Can I measure my PD at home?

Yes. A millimeter ruler and mirror can be used to estimate PD at home. However, professional measurement is generally more accurate, especially when specialized lenses such as progressive lenses are involved. (Cleveland Clinic)

Do I need a different PD for reading glasses?

PD can vary slightly depending on viewing distance and measurement method. If you need dedicated reading glasses or other specialized lens designs, follow the measurement guidance from your eye-care professional or eyewear provider. (Cleveland Clinic)

Can I use contact lens measurements for eyeglasses?

Do not assume that measurements or prescriptions for contact lenses can simply be transferred to eyeglasses. Contact lenses and eyeglasses use different fitting and prescription information.

Use the prescription intended for your glasses.

Can I order prescription glasses online without knowing my PD?

That depends on the eyewear provider and ordering system. Some providers offer measurement instructions or other ways to obtain the required information.

If PD is required for your order and you do not have it, obtain the measurement before submitting your order rather than guessing.

A Simple PD Checklist

Before ordering prescription glasses online:

• Check whether your prescription includes PD.

• Confirm whether you have a single or dual PD.

• Make sure OD and OS are entered correctly.

• Enter SPH, CYL, AXIS and ADD exactly as prescribed when applicable.

• Do not calculate or modify prescription values yourself.

• Follow the eyewear provider's instructions for missing PD information.

• Consider professional measurement when ordering progressive or specialized lenses.

The Bottom Line

PD means pupillary distance, the measurement between the centers of your pupils. It is an important measurement used when positioning prescription lenses, but it is not the same thing as the optical prescription values such as SPH, CYL, AXIS or ADD. (Cleveland Clinic)

If your prescription includes PD, enter it exactly as provided.

If it does not, ask your eye-care professional for the measurement or follow the measurement instructions provided by your eyewear provider.

For progressive or other specialized lens designs, professional measurement can be especially useful. (Cleveland Clinic)

Explore PHANEO Prescription Eyewear

Once you have your existing prescription information ready, you can review available prescription lens options from PHANEO.

Explore PHANEO Prescription Eyewear

Related Reading

How to Read a Glasses Prescription: SPH, CYL, AXIS & ADD Explained

High Bridge vs. Low Bridge Glasses: Which Fit Is Right for You?

Photochromic vs. Transitions Lenses: What's the Real Difference?