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Eyeglasses Size

Eyeglasses size is not important for fitting eyeglasses because eyeglasses are designed so that the temples, nosepads, and bridge can be adjusted to fit properly. Eyeglasses frame size is first and foremost a fashion decision. This article covers two aspects of eyeglasses frame size:

1) How to find the right size of glasses that you want.
2) How eyeglasses frame sizes work and how to measure your frame size

Finding The Right Size Eyeglasses For You

The easiest and fastest way to find the right size glasses for you is to use your current glasses as a benchmark. Once you know the size of your current glasses, you have a frame of reference for a new pair of glasses. So let’s say for example that your glasses have this size: 50-20-145. You can now use the Advanced Search function to search for eyeglasses with a similar size. When you do the search, search the eye size range 49-51, and search the bridge range 18-22, and do not search the temple size. Temple size is really not important except is very special cases. Searching a range of sizes is important because it vastly increases the number of results you will get, and also the difference in sizes will be almost unnoticeable compared to your current eyeglasses.

For any person, there is no one right size of glasses. Your face can accommodate a wide variety of glasses sizes and most glasses will work for most people. In order to understand why this is true, you need to look at what size means; size in glasses is a very different concept than size in shoes or clothing. As a result, you should focus most on how the glasses look on your face; when you find glasses that look good, in most cases the glasses can be adjusted to fit your face.

The rule of thumb is that the total width of the glasses front all the way across, including the endpieces, should be similar to the width of your head. This will allow for the optimum proportion of the glasses to the head, and for the best comfort.

How To Measure Your Eyeglasses Frame Size

There are two ways to measure your eyeglasses frame size:
1) Read the tiny lettering on the inside of your glasses. Sometimes the lettering has worn off, or it is too small for you to see even with a magnifying glass. In which case you need to
2) Measure your glasses with a millimeter ruler. The eye size is measured from one side of the lens to the other, horizontally, at the widest points. The bridge size is the distance between the lenses at the closest point. The temple size is measured from the tip to the hinge, including the bend.

Eyeglasses Sizes

A glasses or sunglasses frame model is usually available in just one size, meaning one combination of eye, bridge, and temple lengths. Occasionally a glasses frame may have more than one size: for example 50-17-135 B40, and 52-17-135 B42, and 54-18-140 B43. You cannot mix and match the measurements, you must take the whole set of measurements for a given glasses frame and you cannot choose a different collection of measurements. For some manufacturers, if a frame model has more than one available temple length, you may be able to swap temples, but you must contact our customer service department to find out if this is possible for the frame you want.


Glasses frames have four basic measurements: the eye, bridge, temple, and B measurements. The eye size refers to the horizontal width in millimeters of one of the frames lenses. The measurement is taken from the inside of one side of the frame to the inside of the other side of the frame. The lens is measured from its furthest point, where it would intersect with a vertical line. The bridge measurement is the distance in millimeters between the two lenses. It is measured between the two closest points of the two lenses.

The temple length is measured along the length of the temple, from one end to the other, including the bend. Many frames are constructed with an endpiece that extends from the frame front back along the line of the temple. This backward extension of the frames endpiece could be as little as 2mm, or as much as 15mm. When the endpiece extends further back, the temple length tends to be smaller to compensate.

As a result, if you are accustomed to a 145mm temple length, a 135mm temple could work perfectly for you if your new frame has an endpiece that extends back 10mm. This is also the case with many sunglasses with a wrap design. The wrap has the effect of bringing the frame front back towards the ears, thereby requiring shorter temples lengths to compensate. The B measurement refers to the vertical height of an eyeglasses lens, and is measured from the tip to the bottom of the lens aperture of the frame. The measurements are taken from a horizontal line intersecting with the top of the lens, to the horizontal line intersecting with the bottom edge of the lens. The B measurement is only important when making progressive or multifocal lenses.

Sport Sunglasses

Reading Your Glasses Size

Most glasses frames have some size information printed on the inside of the frame, although the lettering can be worn away with use. To find all the lettering, you must look on the inside of both temples, and on the inside of the bridge. The numbers usually look something like this:

GU125 635 50 17 135

For this frame, it means that the model number is GU125, color number 635, with size 50-17-135. In this case, the brand Guess is abbreviated GU, followed by the model number of the frame. The eye size is followed by bridge size, sometimes with a small square box in between. The temple length could be printed after the eye and bridge sizes, or elsewhere. Other letters and numbers could refer to the color of the frame. The B measurement is never written on the frame.

Eyeglasses Frame Size – Total Width

However, these sizes do not give you all the information that you need to know for sure how big the glasses frame is. To know truly how big the frame is - meaning how will it look on your face - you must determine the total frame width. The total frame width includes the endpieces, and the endpieces are never measured and specified. The endpiece refers to the width of the frame from the edge of the lens out to the edge of the frame where the temples are connected to the frame front. On the product pages of the Eyeglasses.com catalog, look in the frame details for the “screw to screw” measurement, which tells how wide the frame actually is.

Once you have determined the total frame width, you can use that value to compare to your current glasses, or you can hold a ruler up to your face to get an idea how well the frame will line up with the sides of your head. Endpieces vary in size from 3mm to 15mm each, which adds up to 6mm to 30mm of the total frame width. The rule of thumb is that endpieces add up to about 10% of the total frame width. Here is the formula to determine the total glasses width: Total frame width = left endpiece + left eye size + bridge size + right eye size + right endpiece.

You can quickly estimate the total frame width by adding the left and right eye size and the bridge size, and then multiplying times 1.1. Because the endpiece sizes are never supplied by the manufacturer, and if you do not have the glasses in your hand to measure, there is a way of more accurately estimating the size of the endpieces online:

1. Add up left eye size + bridge size + right eye size (= Value A)
2. Put a ruler up to the photo on your computer monitor to measure the distance of left eye + bridge + right eye (= Value B)
3. Put a ruler up to the photo on your computer monitor to measure the length of one endpiece (= Value C)
4. Do some math: B/A = Value D.
5. Value D times C = Value E
6. Value E = Real value of one endpiece.
7. 2E + A = Total frame width

There are some cases where a large glasses frame on a small head could look oversized, and a small glasses frame on a large person may hurt (as the temples persistently dig into the sides of your head). But even in extreme situations, you choose frames first on how they look on your face.

Adjusting Your Glasses

Almost all eyeglass frames are designed so they can be adjusted. You can take your eyeglass frames to a local optical professional for an adjustment, or read more about adjusting your eyeglasses.

Virtual Try On Application

We have developed a patented Virtual Try On application so you can upload your photo and virtually "try on" most of our frames and see how the size looks on you before you buy.  You may feel that it is necessary to try on glasses before you buy them. However, unlike a shirt that you cannot alter to fit your body, glasses can be adjusted to fit your face. Read more about eyeglasses fit. We have a liberal return policy, so feel free to order some eye glasses online, and then return the ones that you don’t like within thirty days for a full refund (there are some limits here). We do not charge a restocking fee unless you want to order a large number of frames on approval. If you are unsure of a color, or which size of a frame to order, this is a great way to be sure and to see the frames on your face in your own home and take your own time to decide.






Author of this article: 

Mark Agnew, AuthorMark Agnew
CEO of Eyeglasses.com, which he founded in 1999.  For over twenty years, he has educated consumers, improved their vision choices, and reduced costs in eyewear.  Mark authored The Eyeglasses Buying Guide, the most comprehensive and best-selling glasses buying guide in the world.

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