How to measure your PD (Pupillary Distance)
What is pupillary distance?
Pupillary distance (PD) is the measurement, in millimetres, between the centres of your pupils. This measurement is unique to each individual and determines the ideal placement of your prescription lenses for clear vision.
PD can vary depending on whether you’re focusing on distant objects or those up close (long-sighted or short-sighted). As it plays a crucial role in lens design, it’s important to ensure this measurement is accurate. Since everyone’s face shape, eye positioning, and prescription needs are unique, a precise PD measurement ensures your lenses function properly and provide the best vision for you.
If you already know your PD, simply select the correct value from the drop-down menu on the left-hand side of the screen when entering your prescription details on our website.
How is pupillary distance measured?
Pupillary distance (PD) is measured in millimetres from the centre of one pupil to the centre of the other, or across the outer edges of the coloured parts of your eyes. While looking straight ahead, this simple but essential measurement ensures your lenses are positioned correctly, with the optical centre aligned to where your eyes naturally rest throughout the day. For example, if you’re wearing varifocal lenses, an accurate PD is crucial to properly design the lens, ensuring it accommodates its multifunctional purpose effectively.
What is an average pupillary distance?
The average pupillary distance (PD) is typically between 54-74mm for adults and 43-58mm for children.
When measuring your PD, whether for yourself or someone else it’s important to take the measurement a few times to ensure consistency. A single inaccurate measurement, even if it’s off by just a few millimetres, can misalign the optical centre of your lenses, reducing their effectiveness.
If you have a particularly strong prescription, avoid relying on the average as a rough estimate. An incorrect PD measurement can lead to headaches, eye strain, and potential worsening of your vision over time. Accurate measurement is key!
How to measure your pupillary distance.
At the opticians.
If you’re scheduled for an eye test, you can ask your optometrist or dispensing optician to include your pupillary distance (PD) as part of your prescription. However, some opticians may charge for this information or decline to provide it, possibly to encourage in store glasses purchases. If they refuse, don’t worry, you can easily measure your PD yourself!
Measuring yourself at home
The Apps
The two apps that we would recommend are the following;
EyeMeasure is a free iOS app designed to measure Pupillary Distance (PD) and Segment Height with high precision using an iPhone’s camera. It provides instant, hassle-free results with just a quick face scan. The app measures both distance and near PD. No additional tools are required, as it relies solely on your iPhone’s front-facing camera. EyeMeasure is compatible with iPhone equipped with a TrueDepth camera system. Users have praised EyeMeasure for its accuracy, particularly when ordering glasses online. The app is available for free on the App Store
GlassesOn is a free Android app designed to accurately measure Pupillary Distance (PD) using advanced computer vision technology. This medical-grade app allows users to obtain essential eyewear parameters without the need for additional tools. Users can determine their PD in less than a minute by using any standard magnetic card, such as a library card, for reference. GlassesOn is compatible with Android devices running version 9.0 or higher. GlassesOn is available for free on the Google Play Store
A Ruler
1) Stand approximately 30cm in front of a mirror.
2) While facing the mirror, hold a ruler just above your eyebrows.
3) Close your left eye, then position the ruler so that the 0mm mark lines up with the centre of your right pupil.
4) Look straight ahead, then open your left eye and close your right.
5) Your pupillary distance measurement is the number that aligns with the centre of your left pupil.
6) To ensure accuracy, repeat this process 3-4 times.
Measuring someone else at home.
To measure someone's pupillary distance (PD), have them focus on a point straight ahead in the distance with both eyes open. Position the ruler so the 0mm mark is aligned with the centre of one pupil. Be careful not to block their line of sight, as this can affect the accuracy of the measurement. Try to position yourself at a slight angle rather than directly in front of them. Keeping the ruler steady, measure to the millimetre mark at the centre of their other pupil. Repeat this process several times to ensure the most accurate measurement, and record the result.
If you don’t feel confident to do this yourself, we can help you.
Take a photo of yourself wearing your own glasses or someone else’s with clear lenses to help us measure your pupillary distance. Make sure to include the measurements of the front frame in millimetres.
When taking the photo, keep your eyes open and look straight at the camera avoid looking up, down, or to the sides. The photo should be taken from about 1 metre away to ensure your head is in a natural position.
Once you’ve captured the perfect shot, email it to us at [email protected] along with your name, order number, address, and postcode. Our friendly team will review your image and let you know if it’s suitable!
Can Your Pupillary Distance Change Over Time?
Pupillary distance (PD) evolves with physical development, so a growing child’s PD measurement will likely change over time.
However, once a person reaches adulthood, this stabilizes and the PD generally remains consistent. This means that adults typically only need to measure their PD accurately once.
If you have any questions about measuring your pupillary distance or need more information, feel free to reach out. We're happy to assist with any PD related queries you may have!