Measure Pupillary Distance
Measure Your Pupillary Distance (PD)
Your pupillary distance (PD) is the measurement in millimeters between the centers of your two pupils. It's a critical number for crafting prescription lenses that align precisely with your eyes — and getting it right makes a real difference in clarity and comfort.
The best way to get your PD is to ask your optometrist during your next exam. Most doctors measure it routinely and can add it to your prescription upon request.
Measure It Yourself
If your prescription doesn't include a PD, there are two easy options:
Option 1 — Use the EyeMeasure App (Recommended)
EyeMeasure uses your iPhone's front-facing camera to take an accurate, hands-free PD measurement in seconds.
Download EyeMeasure on the App Store →
Option 2 — Use Our Printable PD Ruler
Download & Print the Aldermiller PD Ruler →
Once printed, follow these steps:
Step 1 — Position the ruler.
Stand in front of a mirror. Hold the printed ruler horizontally just above your nose bridge, below eye level. Fold the printout if needed so it sits flat and straight.
Step 2 — Align to one pupil.
Close your right eye. Line up the zero mark of the ruler with the center of your left pupil.
Step 3 — Read the measurement.
Open your right eye and close your left. Read the millimeter mark that lines up with the center of your right pupil. That number is your PD.
Step 4 — Repeat for accuracy.
Take the measurement two or three more times and average the results. A difference of 1–2mm between readings is normal.
Dual PD vs. Single PD
Some prescriptions list two PD numbers (e.g., 32/31) — one for each eye measured from the center of your nose. This is called a dual PD or monocular PD. A single number (e.g., 63) is your binocular PD. Either format works when placing your order.
Questions? Contact us at hello@aldermiller.com and we're happy to help.