How To Measure PD
Pupillary distance (PD) measures the distance between the centers of your pupils and is used to center a prescription lens accurately in your frames. Your optician will usually measure your PD, or you can use our digital PD ruler to measure it quickly online.
Why Is It Important
Every pair of prescription lenses has an “optical center,” which is the spot you naturally look through. To place this correctly, your pupillary distance is used. That’s why this measurement needs to be as precise as possible; it helps your lenses work the way they’re supposed to and keeps your vision clear and comfortable.
About Single And Dual Pd
| PD Type | Also Known As | Definition | Format | Typical Range |
|---|---|---|---|---|
| Single PD | Binocular PD | Distance between the centers of both pupils | One number (e.g., 63) | Adults: 54-74 Children: 43-58 |
| Dual PD | Monocular PD | Distance from each pupil center to the bridge of Nose | Two numbers (e.g., 32/30) | First number = Right eye (OD) Second number = Left eye (OS) |
How To Measure Your Pupillary Distance (Pd)
Step 1
Stand in front of a mirror, and approximately 8 inches should separate you from the mirror.
Step 2
Press a millimeter (mm) ruler up against your forehead.
Step 3
After closing your right eye, line up the center of your left pupil with the 0 mm on the ruler.
Step 4
After maintaining a straight gaze, close your left eye and open your right.
Step 5
Your binocular PD is the millimeter line that extends to the center of your right pupil.
Measuring A Friend’s Pupillary Distance
1. Ask someone else to look at something about 20 feet distant with both eyes open in order to gauge their PD.
2. Line up the 0mm mark with one pupil's center using a ruler, then measure to the other pupil's center.
3. All you have to do is make sure they don't look at you while you're measuring, that you stay out of their line of sight, and that they continue to look straight ahead with their eyes as motionless as possible.
4. To ensure that the measurement you obtain is consistent, repeat this process several times. Adults typically have pupillary distances between 54 and 74 mm.