The Numbers on your Glasses
The Bridge Width
The bridge width is the minimum horizontal distance between the nasal surfaces of the rims on a plastic or metal frame, or the minimum horizontal distance between the nasal surfaces of the lenses in rimless frames.
If a frame has adjustable nose pads on metal arms various modifications can be made in order to achieve a satisfactory fit, see our guide here on how to do this.
The Lens Width
The lens width is the distance between the vertical sides of a rectangle containing the lens shape. The sizes for the lens width and bridge width can usually be found on your current glasses by looking on the inside of the frame
The Arm Width
The arm length is measured from the dowel point to the extreme end of the side, this is made up of the length to the bend and the length of the drop to give the overall length of side.
Overall Frame Width
Another measurement to consider would be the overall width of the frames. Aside from 2x the lens width + the bridge width, the overall width is also dictated by factors such as the thickness of the rim of the frame and how swept out the lugs are.