Choosing The Right Glasses Size

Glasses on shop rack

With thousands of frames to choose from, how do you choose a pair of glasses that will fit correctly?

On this page, you'll learn two methods for choosing a great fitting frame, without having to try them on first.

These tips are extremely handy if you are considering purchasing your next pair of glasses on the internet. If you do decide to buy online, it is advisable to choose a supplier that offers an exchange or return service, just in case!

First, let's take look at the information that is printed on your existing frames.

Each frame is printed with various information (usually on the inside arms). This information contains the Eye size, Bridge size, Arm size, Model number, Colour code and Brand.

Eye, Bridge and Arm Sizes Printed On Glasses

The first numbers we need to look for are the two numbers that are printed on either side of a square box (see image on left). These numbers are usually found on the inside of one of the arms, but in some cases, they can be printed on the back of the bridge or on the inside of the nose piece.

The number on the left-hand side of the square box is the "Eye Size" and is sometimes referred to as the "A" measurement. This is the width of the lens at its widest point measured in millimetres (see A in the diagram below).

The number on the right-hand side of the square box is the "Bridge Size" and is sometimes referred to as the "DBL" (distance between lenses). This is the distance between the two lenses measured in millimetres (see DBL in the diagram below).

I most cases you will find a third, three-digit number, following the eye and bridge sizes, this is the "Arm Length". The arm length is measured in millimetres from the attachment screw to the tip of the arm. The measurement is made before the bend is put into the arm. So, if you were to physically measure your existing glasses, you would measure from the screw to the bend and then the bend to the tip. In some cases the arm measurement is not located alongside the eye and bridge sizes, this is usually the case when the eye and bridge sizes are printed on the back of the bridge or nose piece. However, it will generally be printed on the inside one of the arms (look for a number between 125 and 145).

Measurements which are not printed on your glasses.

When purchasing glasses over the internet there are two further measurements which are extremely useful in helping you choose a good fitting frame. These measurements are not usually printed on your existing frames but, they can easily be measured with a ruler. The first measurement which is particularly useful is the "Total Width". The total width is the overall width of the front of the frame in millimetres (see diagram below). The second measurement is the "Lens Depth" and is sometimes referred to as the "B" measurement. This is simply the depth of the lens measured in millimetres as per the diagram below.

Glasses Front Dimensions DiagramGlasses Arm Dimensions Diagram

Two methods for choosing a good fitting frame.

Now that you understand what all the measurements mean, you're almost ready to start your search. However, it is worth noting that it is very unlikely that you'll match every measurement exactly to your existing glasses. By choosing one of the two following methods you'll be able to find a good fitting frame without narrowing your search too far leaving little to choose from.

Method 1: Using Eye Size & Bridge Size

In many cases, you can achieve great results by comparing the Eye Size (A) and Bridge Size (DBL) to your existing frames. Most online suppliers will allow you to filter their category pages by Eye size and Bridge size and, If you are choosing a similar style of frames to your existing pair, this will generally work very well.

However, bear in mind the Bridge Size is not really the "size of the bridge that fits you", think of it simply as the distance between the two lenses on any particular style. Aviator styles, where the lenses meet very close towards the brow of the frame, have a very small bridge size with a wider eye size yet these can fit just as well as a more traditional style with smaller eye size and wider bridge (see diagram below).

Glasses frame size comparison

The green number in the diagram above is not to be confused with "Total Width" which we will cover later. Using the calculation above you can identify frames which are likely to be a very similar fit to your existing pair, even if the overall style is different.

The Arm Length can also be considered. However, in almost all cases wider frames have longer arms, so use this measurement as a secondary consideration.

Method 2: Using Total Width (Preferred Method)

By comparing the Total Width measurement of your existing frames to those displayed online, you can achieve much better results. That being said, not all online suppliers will display the Total Width of each individual frame as it needs to be physically measured and is not generally not given by the frame manufacturers. If this is the case you can revert to the previous method.

To measure the Total Width of your existing glasses place the frames on a flat surface with the arms opened. Place a ruler on top and at the front of the frame measure the outside edge of the left temple piece to the outside edge of the right temple piece on millimetres.

When choosing your new glasses you may select a frame with a Total Width measurement within 2 to 3 millimetres. Here at Spex4less, you can filter any category page by Total Width and the results shown will be within 2 millimetres of the width that you select. We recommend using the Total Width measurement where possible and reverting to method 1 when the total width is not available. As in Method 1, the Arm length can be used as a secondary consideration.

Lens Depth

You may have noticed that thus far, we have not mentioned the Lens Depth. This measurement will largely depend on the style of frame you decide upon and in many cases, is not required to identify a good fitting frame. However, if you are choosing glasses for Bifocals or Varifocals, be mindful that the shallower the frame is, the less area there will be available for the reading element of your lens. When purchasing Varifocals we recommend a Lens Depth of at least 27 millimetres. For this reason, at Spex4Less, Varifocal lenses will not be available to purchase on frames with a lens depth of fewer than 27 millimetres.

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