What does BC mean when ordering contact lenses?

Q. When I’m ordering contact lenses and it asks for “BC”, what does that mean?

Adam answers:

Base curve, or technically base curve radius. Base Curve, or BC, is the radius of the sphere of the back of the lens, and it is almost always between 8mm and 10mm. You can think of it as the “size” of your contact lenses.

Assuming you have a contact lens prescription from your eye doctor, your base curve should be easy to find.