You’ll just need a ruler in millimeters and a mirror.
Here’s how you can easily measure your pupillary distance:
1. Place yourself in front of a mirror. Ideally at 20 cm away (8 inches).
2. Once in front of the mirror, look straight ahead and place the ruler on the bridge of your nose.
3. With one hand, make sure that the ruler starts (the zero end) in your right pupil.
4. Measure the distance between your right pupil and your left pupil.
5. The number will be your PD, also known as pupillary distance.