Use a millimeter ruler or a PD measuring app
Stand about 8 inches away from a mirror
Keep your head straight and look at your reflection
Close your right eye and align the ruler’s 0 mm mark with the center of your left pupil
Open your right eye and close your left eye
Read the millimeter mark that lines up with the center of your right pupil
Record the distance as your distance PD
Repeat the measurement 2 to 3 times and average the results
For near PD, measure while focusing on a point about 13 to 16 inches away
Ask someone to measure from the center of one pupil to the center of the other if needed
Use a professional eye exam for the most accurate PD measurement