This guide shows the parts of a frame, how to tell size, and how to measure for fit.

FRAME FRONTS & SIZES

In an industry of confusing terms, the front of the frame is actually and refreshingly called the "front". For measurement purposes it has three sections. The first two are used to determine size. Below is a description of each section.

1. The "eye" - This is the part you look through.
2. The "bridge" - This is the nose area
3. The "end piece" - this is the part that extends outward past the "eye". The temple (ear piece) attaches to this.

So, the size of a frame is the "eye" + the "bridge". This distance is measured in millimeters. The combination of these two measurements is referred to as the "eye size". Common eye area measurements range from 45 millimeters to 65 millimeters. Bridge sizes generally range from 18-24 millimeters (mm).

Sizes are written as eye+bridge. For example, 48/22 or 54/18.

The extra width added by the end piece has an effect on the fit and actual size of the frame, but is not measured or recorded. Bummer.

TIP! Sizes are usually stamped somewhere on the frame. Look on the back of the frame at the top of the right eye out toward the end piece. Next, look at the back of the bridge. Look closely. In one of these two areas, you should find a size marked like the sizes I described above. If you don't find a size, chances are you are holding a dime-store frame, probably of low quality and value.

EAR PIECES

These are usually called temples. They are almost always separate pieces from the frame front, attached by hinges at the back of the end piece. Whereas frame sizes are always in millimeters, temple sizes are frequently marked in inches. Go figure.

The size is usually stamped on the inside of the temple.

Thick, plastic, American frames are likely to use inches. 5"-6 1/2" lengths are the typical range.
Thinner temples, metals, and most European and Asian frames use millimeters for temple sizes. 125mm - 140mm is the typical range. Temple sizes are almost always measured along the temple from the temple butt to the end.

OTHER MARKINGS

Frames may carry markings other than the size and temple length, such as manufacturer, desiner, frame name, and color. Sometimes, colors are written as a number. A temple may be marked "3002 013 135". The 135 is the temple length (see above). The other numbers in this case are frame style (3002) and color(013).

If all of this sounds confusing, it really can be, even for some people in the industry. There is no set standard for expressing the physical properties of an eyeglass frame. Every manufacturer has their own system. Hopefully, this explanation will have helped you know:

1. How frame sizes are measured
2. Where to look for them
3. What they mean when you find them
4. To ignore numbers that are not part of the size.

WILL IT FIT?

Now that you can identify frame size, you should be able to find the size on a pair of your existing glasses and use that to shop on Ebay for frames that fit, right? Maybe. The size WILL give you a rough idea of fit, but there is of course more to it than (oh dear) meets the eye.

There are variables beyond the scope of this guide that will affect how an eyeglass frame fits you. Here are the "biggies".

• END PIECES - The extra width of the end pieces (see top of guide) can add substantially to the overall frame width, making it effectively bigger. If you are using sizes taken from an existing frame, compare the end piece width of those frames to the ones you are looking at on Ebay. This will help get you in the "ballpark".
  
• BRIDGES - There are many types of bridges.
  
• Plastic frames have two main types: "saddle" and "keyhole". The frame illustrated at the top of this guide has a keyhole bridge. Like an old-fashioned hole for a skeleton key, the bridge is wide at the top. Support is on the sides of your nose only. Saddle bridges are designed to give even support all around, and do a better job of weight distribution for many people.
• Metal frames usually have small metal arms at the bridge with nose pads attached to the end. These have the advantage of being adjustable, but they also concentrate the weight of the frame in a smaller area. Antique frames, and some modern designer frames inspired by antiques, have saddle bridge - just a flat curve of metal over the nose connecting the two eye areas (eye wires).

Don't let the many variables of eyeglass size and fit warn you away from buying frames on eBay. Remember, better sellers will have liberal exchange / return policies, and your local eyecare professional can adjust the frame for you, usually for free.