There are a number of ways to determine your frame size for glasses or sunglasses. Consider the options below:

1.    Take the dimensions from an existing comfortable pair of glasses

The easiest way to select a suitable frame size is to take the dimensions from a comfortable pair of glasses that you already have. If you look at the inside of the arms on your current spectacles you will see writing displaying the frame manufacturer (not always), frame model code, colour code and 3 measurements. (See photo). The first two measurements will usually be separated by a rectangle – but not always. Alternatively, you might find these measurements are on the inside of the bridge (especially on metal frames) or the inside of the right nose pad on plastics frames. The side length can sometimes be stamped on the inside of the plastic end tips.


The first measurement is the Lens Diameter in millimetres and is measured across the lens from the bridge. In the photo this is 51mm.

1. The second measurement is the Bridge Width in millimetres. This is the area which sits directly above your nose. Smaller measurements will suit narrower bridges whilst larger measurements will suit broader bridges. On most metal frames the bridge width is less important as it can be adjusted to suit nearly everyone. However, many plastic frames cannot be adjusted. In the photo this is 18mm which is standard for most adults.


The third measurement is the Arm Length or is sometimes referred to theside length or temple size in millimetres. Arm length is the overall length of the side measured from the centre of the dowel screw that secures the side to the front, to the end tip, with the drop end or hockey end straightened out. When measuring a frame side it is not necessary to straighten the side to obtain the correct measurement. Simply place the ruler on top of the side and'walk' it around the outer radius of the bend to the tip. Side lengths as a rule tend to increase in 5mm increments. There are three arm lengths that can be regarded as standard for adults; 135mm, 140mm and 145mm. In the photo, it is shown as 135mm.


Though not shown on your glasses, an important measurement is the Frame Width. This is the horizontal distance between the centres of the two dowel screws that secure the sides. As a general rule this can be calculated by taking the lens diameter x 2, add the bridge width and add on 6mm to cover the hinge extensions for both end pieces. In the example above this will be as follow: 51x2 +18+6=126. This works well for glasses but not for sunglasses as wrap lenses tend to be larger and curved to reduce the overall dimensions. At we show all frame widths on the eyewear product pages.

The Lens Diameter and it's shape is a matter of choice, but the bridge width, arm length and frame width determine the fit.

2.    Measuring an existing pair of sunglasses or glasses

The easiest way to work out your frame size is to take an existing pair that you are happy with and measure the frame width (the horizontal distance between the centres of the two dowel screws that secure the sides) and arm length (from hinge to the tip). You can then compare them to the ones on the website.

3.    Measure yourself to determine your frame size


The best way to do this is to look into a mirror and hold a ruler so that it is lined up with your temple (See photo). Then measure in millimetres the distance between your left and right temples. In the photo example, the frame size is 125mm.

Note that when selecting frames, one or two millimetres either way will not make any difference particularly with an adjustable bridge pad or when purchasing wrap sunglasses. In fact, most wrap around sports sunglasses are very accommodating so you can select them based on whether you have a small, medium or large head.

Are sizes different for Sunglasses and Glasses?

In most cases a person's eyeglass frame is smaller than their sunglass frame, however if the styles of the frame are similar then the size might be similar.

Still not sure about your frame measurement?

If the measurement details on your existing frame have rubbed off or you are unsure about sizing please feel free to contact us for advice. We will be happy to talk you through the measuring process.

What frame will suit me?

If you are unsure about whether you will suit a particular design of frame, have a look at our feature on choosing eyewear to suit your face shape