- What is pupillary distance (PD)?
- Monocular vs. binocular PD measurements
- How to measure pupillary distance
- PD measurement: Alternate method
What is pupillary distance (PD)?
Pupillary distance (PD) is the distance between the pupils of your two eyes. It is an essential measurement when buying a new pair of eyeglasses or prescription sunglasses. For greatest comfort and clarity, the optical center of each lens of your glasses should be aligned directly in front of the center of your pupil.
PD is measured in millimeters (mm). The average pupillary distance for an adult is about 63 mm, but this is not a number you’ll want to assume.Pupillary distance can vary widely — roughly between 51 mm and 74.5 mm for women and 53 mm and 77 mm for men.
Monocular vs. binocular PD measurements
There are two types of pupillary distance measurements:
Monocular PD. This is the distance between the center of your pupil and the middle of the bridge of your nose. Monocular PDs are required for accurate fitting of progressive lenses.
Binocular PD. This is the distance between the center of the pupil of one eye and the center of the pupil of the other eye.
Due to facial asymmetry, monocular PDs aren’t always exactly the same. But the sum of your two monocular PD measurements should always equal your binocular pupillary distance.
How to measure pupillary distance
Pupillary distance measurements usually are taken when you are being fitted for glasses after your eye exam. An optician typically will measure your PDs with a high-precision measuring device called a pupillometer.
But let’s say you have your eyeglass prescription and want to buy a stylish pair of eyeglasses online. You need your PD measurement for that.
Don’t worry. You can measure your own PD in a pinch. All you need is a millimeter ruler and a mirror.
Here are the basic steps for measuring your PD:
Stand in front of a mirror (about 12 inches away).
Hold a millimeter ruler horizontally, just above your eyes and flat against your eyebrows.
Close your right eye.
With your left eye, align the ruler’s zero mark to the center of the pupil of your left eye.
Without moving the ruler, close your left eye and open your right eye.
Find the millimeter mark on the ruler that is aligned with the center of the pupil of your right eye. Record this measurement. This is your distance binocular PD.
For reading glasses, subtract 3 mm from your distance binocular PD. This is your near PD.
You may want to repeat these steps a few times to ensure you are consistent with your PD measurements.
PD measurement: Alternate method
If you already wear prescription eyeglasses, here’s an alternate way to measure your pupillary distance. You just need a non-permanent marker for this one.
Wearing your glasses, stand in front of a mirror (about 12 inches away).
Close your right eye.
Using just your left eye, put a small mark on the left lens of your glasses, directly in front of your pupil.
Without moving your head, close your left eye and open your right eye.
Using just your right eye, put a small mark on the right lens of your glasses, directly in front of that pupil.
Take off your glasses and measure the distance between the two dots on your glasses. This is your distance binocular PD.
Note: Do-it-yourself PD measurements frequently are not as accurate as the pupillary distance measurements taken by a skilled optician. For best results, have an eye care professional measure your pupillary distance (PD) before buying new glasses.
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Page published on Saturday, August 24, 2019
FAQs
Have your friend hold the ruler up to your right so the zero end lines up with your pupil. Measure the distance from your right to your left pupil. The number that lines up with your left pupil is your PD. Smart tip: Just to be sure, measure a few more times to make sure you get the same number.
How do you measure pupil distance accurately? ›
Have your friend hold the ruler up to your right so the zero end lines up with your pupil. Measure the distance from your right to your left pupil. The number that lines up with your left pupil is your PD. Smart tip: Just to be sure, measure a few more times to make sure you get the same number.
What if PD is off by 2mm? ›
Pupillary Distance (PD) And The Importance Of Having An Accurate Measurement. Did you know that an error of only 2mm can lead to a loss of more than 40% of your clear vision field? PD, or pupillary distance, refers to the distance in millimeters between the center of one pupil to the center of the other.
Is it better to over or underestimate pupillary distance? ›
A precise PD ensures that you experience optimal visual clarity, and any deviation from the accurate measurement may lead to discomfort or difficulty focusing.
What is the PD pupillary distance rule? ›
Using a ruler, line up the 0mm mark with the centre of one pupil, then measure to the centre of the other. You just need to make sure that you stay out of their line of sight, they keep looking straight ahead with their eyes as still as possible, and that they don't look at you while you're measuring.
What if PD is off by 4mm? ›
If the PD measurement is inaccurate, it could leave you looking off-centre in the lenses, potentially leading to eye strain, headaches, blurred vision and even seeing double.
Can I measure my PD with my phone? ›
EyeMeasure enables you to measure your Pupillary Distance (eye to eye) & now Segment Height instantly at near and far distances. No mirrors, credit cards, tape measures or objects needed. It's accurate to up to 0.5mm for the perfect prescription glasses.
What if PD is off by 1mm? ›
Does pupillary distance have to be exact? The pupillary distance measurement does not have to be 100% precise to be applicable, as it can tolerate a small error range. A PD difference of 1mm is not going to cause too much discomfort, and would not be noticeable.
How do I know if my PD is wrong? ›
If you're wearing glasses made using an incorrect PD measurement, you'll probably notice symptoms related to the misalignment. Those include eyestrain, headaches and distortions in your vision. These symptoms aren't dangerous, but they also aren't pleasant.
Does your PD have to be exact? ›
Actually, the pupillary distance measurement does not have to be 100% precise to be useful, as it can tolerate a fairly small error range. A PD difference of 1mm is not going to cause trouble, in real terms, 2mm is a variance of 1mm to each eye, and would not be noticeable.
Don't worry if your glasses prescription doesn't include your PD, we can show you how to measure it by yourself at home. It's easy to measure PD online — all you need is a mirror and our printable ruler, available to download below. You can also measure friends' sizes and have them assist with telling you yours.
What if I was given two numbers for pupillary distance? ›
Dual PD measures the distance between the center of each pupil to the bridge of the nose. That means this measurement has two numbers—the first number is the measurement for the right eye (OD), and the second is for the left eye (OS). A dual PD measurement is usually written like this: 31/30.
What is the average PD for a woman? ›
The average PD measurements for women is 62mm and for men 64mm. Between 58 and 68 is quite normal though. We do encourage you to ask your optician for your PD measurement.
How to tell if pupillary distance is wrong? ›
If you're wearing glasses made using an incorrect PD measurement, you'll probably notice symptoms related to the misalignment. Those include eyestrain, headaches and distortions in your vision. These symptoms aren't dangerous, but they also aren't pleasant.
How accurate does PD need to be? ›
A PD difference of 1mm is not going to cause trouble, in real terms, 2mm is a variance of 1mm to each eye, and would not be noticeable. if you wear glasses with incorrect pupillary distance, you might feel headaches, eye strain and dizziness.
Why is my PD not on my prescription? ›
Pupillary distance is mostly used for sizing your glasses. Your eye doctor might use PD to check parts of your vision or eye function, but it's not usually important for managing your vision treatment. That's why it's not on your prescription even though you need it when you're ordering glasses.
How to measure PD without a ruler? ›
PD Meter App by GlassifyMe
GlassifyMe's PD Meter App is available for both iOS and Android. All you need is a standard card with a magnetic strip (gift card, rewards cart, or points card) and you can measure your PD using the app in a few quick steps – without the need of a ruler.
