How to Measure PD with a Ruler in the Mirror
A clear, step-by-step guide to measuring your own pupillary distance manually.
If you don't have access to a digital sizer or want to double-check an optical measurement, you can measure your Pupillary Distance (PD) yourself using a standard millimeter ruler and a household mirror.
Need a Millimeter Optical Ruler?
Don't use a heavy metal workshop ruler. Print our free calibrated paper template with a nose bridge cutout designed specifically for self-measurement in the mirror.
Step-by-Step Instructions
Position Yourself
Stand in front of a well-lit mirror at a distance of about 8 inches (20 cm). Hold the millimeter ruler flat against your forehead or nose bridge, directly above your eyelashes.
Align the Zero Mark
Close your Right eye and look directly at your left eye in the mirror. Align the 0 mm mark of the ruler with the exact center of your Left pupil.
Read Your Measurement
Without moving the ruler, open your Right eye and close your Left eye. Look directly at your right eye in the mirror. Read the millimeter mark on the ruler that lines up with the center of your Right pupil.
Repeat and Average
Write down the number. Repeat this process at least three times. If you get slightly different numbers, calculate the mathematical average to use as your final Binocular PD.
Crucial Tips for Accuracy
Do not tilt the ruler: Keep the ruler perfectly horizontal. If it is angled, the measured distance will be stretched, indicating a wider PD than you actually have.
Look straight ahead: Keep your head completely still and avoid looking at the ruler ticks while lining it up. Look directly at the pupil center of the open eye.
Skip the Ruler Completely
Measuring yourself manually can be frustrating and error-prone. Try our free online webcam app for a fast, automated, AI-calibrated sizer measurement.