How to Measure Eyeglass Frames

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Not so many years ago, a veil of secrecy shrouded everything about eyeglasses. Prescriptions and frames eluded the average lay person so you had to place the fate of your new eyeglasses in the hands of someone you had never seen before.

So after your exam and getting the prescription you couldn’t read, you had to pick out a pair of frames to hold them. As if that weren’t enough, you had to let someone take a variety of measurements of your eyes and around your face. Unless you asked, you had no way of knowing what they were measuring or why.

Then came the internet. Suddenly, if you had your prescription with all the appropriate numbers and letters, you could order an appropriate frame online. But there seemed so many measurements to take. And what if you got it wrong? And, why all the measurements in the first place? Couldn’t they just slap your new lenses into a frame that you liked?

Not really. While the prescription is important, so are the frame measurements. No matter how perfect the lenses are for your eyes, they will do you no good unless they sit in just the right place in front of your eyes.

Remember, a lens has a particular job. It must funnel the light from images we see, into the pupil so that it falls on just the right spot on the cornea. When it falls in the perfect spot, the focal point, we see clearly. We need glasses to correct any deviations from that because of eye shape or other condition.

So, the lenses meant to correct the lack of perfect focal point must sit in the right position in front of the eye. That’s why it’s so important to get the measurements on the eyeglass frames correct. Basically, there are six basic measurements: eye size, bridge size, temple size, frame width, lens height, and pupillary distance. And if you already have a pair of glasses, this job is so much easier.

Begin with the Old

If you already have a pair of glasses that fit you well, begin with them. Odds are you purchased them a few years ago before buying eyeglasses online became so common, and so an optician fitted you with these glasses; therefore, you already have a start on your measurements.

Take a look at the inside of one of the arms. You should see three numbers there. The first one indicates eye size. That is the space from one side of the frame of one eye to the other side of the frame of the same eye. This measurement is in millimeters.

If you’re a smaller person, you probably want a frame that will accommodate a slightly smaller lens. Eye sizes come in small, medium, and large. Less than 50 millimeters is considered small. Medium is between 51 and 54 millimeters. Large is over 55 millimeters. So when looking at frames, consider the width of your lenses and whether that size with will be the right size for your face.

Then, you will most likely see a small square that serves to separate the first two numbers. This second number indicates bridge size. This is also in millimeters and is the measurement of the space across the bridge of your nose.

If it’s too wide, the lenses of your eyeglasses will not sit in the right position for optimum vision correction. If it’s too small, it will feel very uncomfortable.

The third number you see there is the measurement of temple size. That measurement tells you how long the arm of the frame must be. Remember, it has to be long enough so that the curved portion will reach your ear and rest comfortably there. If it’s too long or too short, it will feel awkward or rest crookedly. In either case, it will throw your vision off kilter.

There are four common temple sizes: 135, 140, 145, and 150 millimeters. Pick a frame that has a temple size that most closely reflects what you need.

Choosing the New

When looking online or in a retail outlet to purchase a pair of eyeglasses, you also need to consider a few other measurements. The first one is total width of the frames. Choose a frame that is only slightly wider than your face. If you have more than finger’s width between the temple and your face, look for something smaller. Otherwise, the most prominent feature of your face will be your glasses and not your attractive visage.

Take a look at lens height as well. This is often called the “B Measurement.” If the frame measures more than 25 millimeters in height, you have a better chance of getting progressive lenses to fit.

Pupillary distance is also very important. Looking in the mirror, take a millimeter ruler and place it over the bridge of your nose. Measure the distance between your two pupils (the little black dots in the middle of your eyes) when looking straight ahead. The center of your eyeglass lenses should fall right over your pupils.


It may sound like a lot to think about when choosing just the right frames for your eyeglasses, but it’s all really a matter of common sense.

In the final analysis, you need to know a few basic measurements: eye size, bridge size, temple size, frame width, lens height, and pupillary distance. Measure them all with a millimeter ruler. Record your measurements and keep them for future reference. Use them when purchasing eyeglass frames online.

You can also use them if you decide to go to an optician or other retail store to help fit you with frames appropriate for your prescription. While they are the professionals, it’s always good to know a little bit about their skill. It will help you hold an intelligent conversation about what they’re doing and ask the appropriate questions.

This is not hard; it’s just a matter of measurements. Choose frames in the appropriate sizes then pick the one you like best. Or, you can choose a smashing and stylish frame and order it in the right size. Either way works.

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