Spectacle Frame Measurement and Sizing

A simple guide to spectacle frame measurements and sizes.


In most cases if you look on the side of the arms of your glasses (on some farmes the measurements are found on the back of the glasses nose bridge), you’ll find some numbers for example as in the picture below:

52 21 140

 (C2 -is a model colour)

These numbers give you the size of your spectacle frame:

In the example shown above the measurements (52 21 140) are all in millimetres

52 is the diameter of the lens,
21 is the width of the spectacle frame bridge
and 140 is the arm / or side length

The diameter of the lens is the width of the lens measured from the nose bridge.
The shape and size of your spectacle frame is ideally determined by your frame style and spectacle prescription, but there is also your own style and fashion choices.


The width of the bridge measurement is the space above your nose between the spectacle lenses. It's necessary to get this measurement correct, too wide and your glasses will be slipping down, too narrow and your spectacles will be uncomfortable.

The arm/side length generally ranges between 135mm - 145mm on adult spectacle frames. Ideally the arms of your glasses should be long enough to comfortably fit over your ears.

With hundreds of frame styles to select at the Little Spectacle Shop, it can be difficult to choose which size is best for you, but we make it much easier with our face shapes and spectacle frame guide here.
Don't forget you can also get a good idea of your frame size, by checking the measurements of any existing comfortable glasses you are currently wearing.