A guide to understanding the frame measurements on your eyeglasses.
If you're buying a new pair of glasses or sunglasses online you need to know the correct frame size for you in order to ensure the perfect fit. Fortunately, if you're an existing glasses wearer it's easy to find this information on your current frames. In this handy guide we'll give you all the information you need to know to ensure your buying experience is hassle free.
If you're a glasses wearer you may notice some numbers on the arms or the bridge. These numbers usually include the frame model, colour code and measurements, as illustrated.
The numbers, 55  18 - 145 (in millimetres) displayed in this image indicate the following:
Our video guide below will help you find these numbers.
The diagram below illustrates the fundamental elements and component parts which make up the spectacle frame. In terms of the fitting of the spectacle frame, the bridge is perhaps the most important part to consider when choosing your frames, because it is here that the major bearing surface and area of contact between the front and the face is situated. The bridge design should facilitate a comfortable and supportive fit which will maintain the position of the lenses over your eyes with a natural gaze.
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 on how to do this.
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 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.
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.