You’ll need to know your child’s PD when ordering new glasses online from Potato Glasses. Don’t worry if your child’s prescription doesn’t include a PD — we’ll show you how to measure it at home, step by step.
It’s easy to measure PD for kids. All you need is our printable ruler, available to download below, and a parent or another adult to help with the measurement.
If you’ve ordered prescription glasses for your child online before, you may have wondered, “What is my child’s PD and how do I measure it?” You can sometimes find your child’s pupillary distance, also called interpupillary distance, on their prescription, but if it’s missing, we’re here to help.
What Is Pupillary Distance (PD)?
Pupillary Distance (PD) is the distance, measured in millimeters, between the centers of your child’s pupils. This measurement ensures lenses are positioned correctly for clear and comfortable vision.
If your child’s eye care professional didn’t include this number on the prescription, don’t worry — you can easily measure it at home. Simply download and print our PD ruler, then follow the easy steps to measure your child’s pupillary distance with confidence.
How to Measure PD for Children
If you’re using our PD ruler to measure your child’s PD, fold it to the side that says “Using a friend.”
Have your child sit comfortably and look at an object about 10–20 feet away to help keep their eyes steady.
Step-by-step PD measurement
Next, place the PD ruler gently against your child’s forehead and line up the zero with the center of their right pupil.
The number that lines up with the center of their left pupil is your child’s PD. When taking the measurement, it can help to close one of your eyes so you can read the number more accurately.
Take a moment to relax your child, then measure their PD a few times to get the most accurate result. If the numbers are slightly different each time, simply use the average as the final measurement.
For example, if you measure your child’s PD five times, add all five numbers together and then divide by five. This gives you your child’s final, average PD.
How Do I Find My Child’s PD for Glasses?
Your child’s interpupillary distance (PD) is important because it helps make sure the lenses are centered correctly over their pupils. This proper alignment supports clear, comfortable vision — especially for children who need stronger prescriptions.
Your child’s PD may or may not be listed on their eye prescription. Most often, it’s written as one number, such as 55.
Sometimes, if there’s a small difference between the center of each eye, the PD may be shown as two numbers, like 26 and 27, which represent the measurement for each eye separately.
What’s the Average PD for Kids?
For children, pupillary distance (PD) changes as they grow, so there isn’t one “normal” number that fits every child. In general, kids’ PD measurements are smaller than adults’ and increase gradually with age.
That’s why it’s important to measure your child’s own PD, rather than using an average. Every child’s eyes are unique, and using the correct PD helps ensure their glasses fit properly and provide clear, comfortable vision.
Single PD vs. Dual PD for Kids
Most children only need a single PD, which measures pupil to pupil.
Single PD
One number that measures the distance between the centers of both pupils. This is the most common PD format for kids.
Dual PD
Two numbers measured from the nose to each pupil. This may be used when each eye needs a slightly different measurement.