1

Take a credit card

This is the approximate width of a Standard Size lens.

2

Stand in front of the mirror

In front of a mirror or a webcam, place one edge of the credit card at the center of your nose. Where does the other edge end?

3

If note touches the end of the eye

A

If the edge of the credit card ends at the end of the eye your fit should be Standard Size

B

If it extends well beyond the end of the eye you should get a Small Size

C

If instead the credit card does not reach the end of the eye then go for a Large Size.