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Jun 19, 2023

How to Measure Pupillary Distance (PD)

Pupillary distance is the space — measured in millimeters (mm) — from the center of one pupil to another. When you need glasses, an optometrist or an optician will measure this distance to make sure

Pupillary distance is the space — measured in millimeters (mm) — from the center of one pupil to another. When you need glasses, an optometrist or an optician will measure this distance to make sure your eyeglasses have the best function and fit for you. If you are ordering eyeglasses online, you may need to measure your pupillary distance, or PD, yourself. Keep reading to learn how.

Simply stated, pupillary distance (PD) is the measurement of the distance between your two pupils, and it helps make sure you eyeglasses will fit and align correctly with the center of your eyes. This alignment and how the glasses are positioned on your face is important when comparing the function of glasses used for seeing things that are far away versus seeing things that are close to you.

Eyeglasses that are not fitted with the correct PD measurement can lead to concerns like:

No one has the same exact eyes as anyone else, but there are some standard ranges when it comes to pupillary distances.

Some medical experts estimate that the average PD range is:

If you are ordering eyeglasses online, there are several ways to measure your PD from home.

If you have a ruler and a mirror or helper, you can measure your PD at home.

If there is someone who can help you, it might be easier to have someone else measure your PD for you. If you need multifocal lenses, you should also measure the individual distances from the center of each pupil to the bridge of your nose.

Take your measurement several times to make sure it’s accurate. Be sure to look straight ahead while taking the measurement.

If you don’t have a ruler, the online supplier for your glasses may offer a printable option. You can also cut a piece of paper or cardboard and mark the center of your pupils, then measure that distance if you are having trouble using a ruler and mirror.

A 2014 study showed that some websites offer technology that will measure your PD for you. There are apps or programs to take a photo of your face and measure your PD that way.

You can also call your optometrist or eyeglasses provider and ask for a copy of the measurement.

Your PD can’t be found on your actual eyeglasses. Hamilton Eye says that the three numbers you see on the arm of your eyeglasses frame provide information on the:

There are a few specifics when it comes to how your pupillary distance is measured. Your gaze naturally shifts inward or outward depending on whether you are looking at things close up or far away. For this reason, Eye Influence says that your optometrist or an optician may measure two types of PD — far and near.

Eye Influence also says that your measurement may change based on what types of eyeglasses you need.

Your optometrist or optician will know that your pupillary distance needs to be measured differently. If you are ordering eyeglasses online, you should be asked for additional measurements based on your prescription.

While PD is an important measurement when it comes to the fit and function of your glasses, it’s not technically a part of your vision prescription or eye examination. Your eye examination will be performed by an optometrist in most cases, and your PD may be measured by an optician — the provider that creates the right eyeglasses to fit your prescription.

Measuring PD is especially important when you need multifocal lenses like bifocals. In this case, you may also need to measure vertical distances and more to find the right fit. In many cases, the measurements needed to ensure the right fit for your eyeglasses are set by the manufacturer of those lenses.

When you are ready for a new pair of glasses, you or the provider who is creating your eyeglasses, will take several measurements to make sure the fit and function are appropriate for your needs. Pupillary distance measurements check the distance between the center of each pupil, and it’s important to measure this distance correctly to prevent complications like headaches and blurred vision.

If you are ordering glasses online, you will need to take this measurement yourself or with the help of a friend. Be sure to take the measurement several times to make sure you have the most accurate result.