When preparing to get a new pair of glasses, you might encounter the abbreviation "PD" on your prescription slip, or be asked to enter your pupillary distance while browsing frames online. If these technical terms seem unfamiliar to you, don't let them cause you any stress—most people have never heard of them before getting their first pair of glasses.
Simply put, your pupillary distance is the measurement between the centers of your two pupils. This is a crucial piece of data, as it determines exactly where the optical centers of your lenses should be positioned to ensure that your vision is both clear and comfortable.
This guide will explain what pupillary distance is in the simplest terms possible, and teach you how to measure it yourself—easily and accurately—using common household items or with the help of our simple online tool.
What is Pupillary Distance?
Simply put, Pupillary Distance (abbreviated as PD) refers to the distance between the centers of your left and right pupils, typically measured in millimeters (mm).
While an ophthalmologist or optometrist will use specialized precision instruments to measure this value during an eye exam, it is sometimes omitted from your prescription slip. Don't worry—although data obtained via professional instruments is the most precise, you can also use simple, reliable methods to measure it yourself when necessary.
Why is Pupillary Distance Important?
Every eyeglass lens has an optical center—the specific point where vision is clearest and the image appears most true-to-life. The purpose of the pupillary distance measurement is to ensure that the center of your pupil aligns perfectly with the optical center of the lens. If the measurement is incorrect and the lens center is misaligned with your pupil, you may experience distorted vision, eye strain, or even dizziness. An accurate pupillary distance ensures your glasses perform at their best and are comfortable to wear.
Single PD vs. Dual PD
When entering your data, you may encounter two different formats:
Single PD (Total Distance): This is the most common format. It measures the direct linear distance between the center of your left pupil and the center of your right pupil.
Dual PD (Monocular Distance): This format measures the distance from the center of each pupil to the center of the bridge of your nose, separately for the left and right eyes. You will end up with two numbers (e.g., 31/30). If you are ordering multifocal or progressive glasses, these separate left and right measurements provide greater precision.
Tip: Most eyeglasses can be fitted using either of these two data formats. However, if you are ordering reading glasses (for presbyopia), you should typically subtract 3 mm from your total measured PD (or 1.5 mm from each monocular measurement), as your eyes naturally converge inward when focusing on objects at close reading distances.
What is a Normal Pupillary Distance?
People often ask: "Is my pupillary distance normal?" In reality, much like height, there is no single standard value for pupillary distance.
Although the average PD for adults typically falls between 60 and 64 mm, everyone has a unique facial structure and spacing between their eyes. Therefore, provided the measurement was taken accurately, whatever value you obtain is considered normal for you.
How to Measure Your PD at Home?
If you want to accurately measure your PD at home, the process essentially boils down to just two steps: find a ruler with millimeter markings, and then measure the distance between the centers of your two pupils. While this sounds simple, there are a few handy tips to keep in mind during the process to ensure the data is precise.
Regardless of which method you choose, we recommend repeating the measurement three times and using the most consistent result.
Special Note: If your eyeglass prescription includes prism correction, for the sake of your visual health, we strongly recommend having your PD measured by a professional eye doctor or optometrist rather than attempting to do it yourself.
1: Using a Mirror and a Ruler
This is the most commonly used method for self-measurement. You will need a clear mirror and a ruler marked in millimeters.
- Step 1: Stand in front of the mirror, maintaining a distance of approximately 20 centimeters (8 inches).
- Step 2: Stand tall and look directly into the mirror, holding the ruler horizontally just below your eyebrows.
- Step 3: Close your right eye, then adjust the ruler so that the 0-millimeter mark aligns precisely with the center of your left pupil.
- Step 4: Keep the ruler perfectly still; open your right eye and close your left eye.
- Step 5: Check the measurement mark on the ruler that aligns with the center of your right pupil. This millimeter value is your pupillary distance.
2: Enlist a Helper (Friend or Family Member)
If you have someone to assist you, the measurement process becomes much easier, and the resulting data is often more reliable.
- Step 1: Relax your body and look straight ahead at a fixed object located approximately 3 to 6 meters away; try not to move.
- Step 2: Ask your partner to hold the ruler horizontally across your brow line and align the 0-millimeter mark with the center of one of your pupils.
- Step 3: Ask your partner to read the measurement mark on the ruler that aligns with the center of your other pupil. This value is your pupillary distance.
3: Using a Marker, Your Glasses, and a Ruler
If you currently have an old pair of glasses handy, this method offers a very intuitive way to measure your PD. Remember to use an erasable marker so that the lenses can be easily cleaned after the measurement.
- Step 1: Put on your glasses and fix your gaze on a small object located at least 6 meters away.
- Step 2: On the right lens, place a dot directly over the position of the object you are viewing.
- Step 3: Repeat the same procedure for the left lens. When you look at the object with both eyes open, the two dots on the lenses should appear to merge into a single point within your field of vision.
- Step 4: Remove your glasses and use a ruler to measure the distance between the two dots on the lenses. This is your Pupillary Distance (PD).
Conclusion
Now, everything is set—all that's left is to choose that perfect new pair of glasses that truly captures your heart!
If you're still hesitating between different styles, why not start by exploring our extensive range of frame designs? Whether you prefer a classic, understated look or are seeking a trendy, avant-garde style, we have something to suit every aesthetic.
Even better, you can make use of our virtual try-on feature right now. No need to leave the house—simply turn on your camera to instantly see exactly how different frames look on your face. Go ahead and start shopping—let your new glasses light up your new look!
