If you’re ordering prescription glasses, getting the right pupillary distance (PD) measurement is the secret to seeing things clearly.
The secret to achieving flawless lenses in your eyeglasses? It all boils down to precisely measuring the distance between your pupils. Think of your pupils as tiny bullseye markers, indicating precisely where the lenses should be placed. A misalignment here can lead to a hazy world.
But how do you measure your pupillary distance? Let’s see!
What is pupillary distance?
Pupillary distance (PD) is the precise measurement, in millimeters (mm), of the distance between your pupils. Achieving an accurate PD measurement is crucial for ensuring that your glasses’ lenses are expertly cut and positioned precisely where your eyes require them.
An incorrect PD measurement may lead to uncomfortable blurriness, potentially causing eye strain or headaches.
How to measure pupillary distance?
There are two types of pupillary distance:
- Binocular (or single) PD is the distance between the center of both pupils.
- Monocular (or dual) PD is the distance between each individual pupil to the bridge of the nose.
How to measure PD by yourself
- Find a ruler with millimeter increments or print out a specialized downloadable PD measurement ruler available through most online eyeglass retailers.
- Stand about 8 inches from a mirror. If you’re using a print-at-home PD ruler, center the zero of the ruler over the bridge of your nose. Make sure the ruler is as level as you can make it.
- Look straight ahead and close one eye.
- Jot down the number on the millimeter mark over the center of the pupil. Repeat this step for the other eye.
Pro tip: If you’re using a regular ruler, stand eight inches from a mirror and hold the ruler level across your forehead. Line up the zero with the center of one of your pupils. Close your other eye and note the millimeter line over the center of the bridge of your nose. Repeat those steps to measure the PD of the other eye.
If you have someone who can lend a hand, follow these steps:
- Ask them to stand directly eight inches in front of you.
- As you hold either the ruler or the PD measure printout above your head, focus on something about 10–20 feet away.
- Have your friend either take the measurement themselves or snap an eye-level pic so you can both take a look.
Practice, practice, practice
Whether you’re measuring on your own or with a friend, repeat the steps at least three times to ensure you get an accurate result. If you’ve taken your measurements five times and gotten five slightly different results, no problem. Just deploy those grammar school math skills and take an average of your measurements.
If you’re taking a PD measurement of each individual eye to the center of the bridge of your nose, each measurement will probably be somewhere between 24–37 mm.
- Remember, if you’re using a ruler, line up the zero with the center of your pupil.
- If you’re using a printed PD measuring tool, line up the zero with the center of the bridge of your nose.
Life hack: A few free apps measure PD, but watch out. Some of the results from these digital tools can be a little off, so read the app reviews and user comments closely.
See an optician
Lens prescriptions don’t typically include a pupillary measurement. The responsibility for this measurement falls on the person fitting the glasses, not the optometrist or ophthalmologist. Even in cases of progressive or bifocal lenses, near PD is usually not required, but the segment height is crucial.
However, you can ask an optician to help you measure your PD.
How do I measure my pupillary distance at home?
Use a specialized print-at-home PD rule or a regular ruler with millimeter increments. Remember, no one’s face is perfectly symmetrical, so go for the monocular (or single) PD measurement. This is the distance between the center of each pupil and the center of your nose’s bridge.
What happens if PD is wrong on glasses?
If your PD is wrong, the lenses of your glasses won’t be centered on your pupils, and your vision might be blurry. Not only is that annoying, but it can give you wicked headaches.
Your pupillary distance (PD) is key to getting perfect prescription glasses and clear sight. Using a ruler or print-at-home PD tool, you can measure your PD at home alone or with a friend’s help. A wonky PD measurement means fuzzy vision and potential headaches, so take your time and get it right.
Of course, your best bet might be going to an optician who can measure them for you.