Stand in front of a mirror
Hold a ruler horizontally against your brow line
Close your right eye
Align the ruler’s zero mark with the center of your left pupil
Open your right eye and close your left eye
Read the measurement at the center of your right pupil
Repeat the process a few times and average the result
Measure in millimeters
For near PD, measure at your usual reading distance
For distance PD, measure while looking at a distant object
Ask someone else to help if needed
Use a PD app or online tool if you do not have a ruler
Get your PD measured by an optician for the most accurate result