For the majority of frames, the standard size we sell will probably be the right size.
Frame measurements can be found on the inside arms of every pair of glasses. The first number refers to the lens width, the second number refers to the bridge width and the third number refers to the side length.
These three numbers (52-18 140 for example) are written in millimetres and represent; the lens diameter, the bridge width and the length of the temple.
If you are still unsure about which size to buy please get in contact with us at email@example.com.