How to find your eyeglass frame size can be one of the more elusive tasks in frame selection. Generally, eyeglass frames are offered in 1 to 2 sizes, determined by style, whether it’s specifically for men, women, children or a unisex design. The manufacturer will ultimately decide on the best-selling option. Ear piece lengths are usually standardized to the sexes and corresponding frame front size.
A popular exception are drill-mounted rimless frames. There is no actual frame surrounding the lenses, this allows the optician to create custom shapes and sizes. Your only concern would be whether the ear pieces come in the length you need for a good fit. A skilled optician can shorten most metal ear pieces that are too long, but being too short is a problem.
To minimize lens edge thickness in high near-sighted prescriptions, select a lens size that’s as small as you are able to comfortably wear.
High far-sighted prescriptions are not usually suitable for drill-mounted styles because the lab must increase the thickness of your lenses to keep the edges from becoming too thin to drill and mount.
Keep in mind that your prescription and choice of lens material will affect your frame choice.
You can find the frame measurements for prescription eyeglasses printed or engraved on either the inside of the ear piece or the bridge area. With sunglasses, sometimes there are measurements, many times not.
The numbers are read in millimeters. The first set of numbers, called eye size, is the horizontal measurement of one lens at its widest point. The second number is the bridge width or horizontal measurement of the bridge. Two examples of how these might appear are: 50/18 or 50□18.
Ear piece length, called temple length, may not always be printed. It would appear as a three digit number, ranging from 115-150, again in millimeters. The remaining information seen on the ear pieces are model and color numbers or frame, collection and/or designer name.
Achieving a Good Fit
Checking for a good fit is well worth the effort, but is only possible if you can physically try them on. You can guess-timate, as I call it, when ordering frames online, but it’s not always ideal. I’ve provided an approximate formula below.
When trying on metal frames, with individual nose pads, make sure the nose pads rest on either side of your nose without the bar of the frame hitting the top of your nose.
When trying on plastic frames, make sure there’s less pressure on the top of your nose and more on either side. This will help you avoid red marks and discomfort.
For ear piece length, the bent or curved area of the ear piece should meet at the top of your ear. If they are too short, there won’t be enough length to go down behind your ear, causing them to pop-up. If they are too long, there will be too much distance between the back of your ear and the end of the ear piece, causing your eyeglasses to slip down your nose.
Some frame adjustments can be made to compensate for a poor fit, but please go to a skilled optician, as home adjustments can weaken or break your frame.
My “Guess-timate Size Formula”
Eye size + half of bridge size + 5 mm (metal frames) or 7 mm (plastic frames)
Use a metric ruler, hold in a horizontal position and place the zero mark evenly between your eyebrows. Look into a mirror and view the number that is aligned closest to your temple.
For example; I’m an average sized 5’ 8” woman with a measurement of 65 mm.
My current frame has a printed measurement of 52□16 and are made of plastic.
Eye size 52 mm + half the bridge size 8 mm + plastic frame 7 mm = 67 mm
Summary of Results
My face measurement is 65 mm and my current frame is 67mm. The extra 2mm difference in the measurement insures the frame isn’t too big or too small. It also shows that it’s a slightly larger frame which is the current fashion trend. The larger style works great with my progressive lenses.
This is only an estimate. The actual frame material and/or design thickness, the part beyond the lens area, will affect the overall width of a frame. This formula uses 5mm and 7mm estimates taken from several current (2015) frame designs.