I recently had a conversation with a friend, who was deciding between a couple of different frames.

This got me to thinking, we never really explain the numbers on the temples of your glasses.  Each one of those numbers means something.  And here is that explanation…

Breaking Down the Numbers

Almost any frame  you could find (that can handle an actual prescription lens) will have these numbers somewhere on it.  Typically, they are on the temple, but occasionally, you might find the first two numbers from the image above printed on the lens-facing side of a plastic nose pad.

The first number listed, refers to the eye size.  So, what does eye size mean exactly?  It’s the width of each lens, at the widest point, in millimeters.  This number always describes the width of a single lens.

You’ll note the first number from the first image was 53.  As you can see above, the lens measures 53 mm using my PD stick (sidebar: PD stick is short for Pupilary Distance, since this is our time-tested way of measuring the distance between your eyes).  I’m going to come back to something here later, so hold onto this info…

This brings us to that second number.  Sometimes it’s listed after a dash, or a box, but it’s always the smallest number.  And it refers to the distance between the lenses.

In this case it was 20, and you’ll notice in the photo it’s also 20 mm.  The important thing, for you, the patient, is that this number does not refer to the space your nose fits in, but the space between the lenses.  If you have a narrow nose and need a small slot for your nose to sit in, that doesn’t necessarily rule out a 20 mm size.  It all depends on how much plastic or nose pad arm is built up there in the middle.

Finally, that big number at the end.  This actually refers to the length of the temple.  If  you have more petite features, you’ll want this to be closer to a 135.  if you’re a big individual, you may  need a 150 or even bigger.  The vast majority of frames out there come with a 140 mm temple, and this will work fine for most adults.

The Big Picture

While these numbers can all be important in finding the right fit for your face, it never tells the full picture.  As stated earlier, the way the frame is put together can change what fits dramatically.  With the frame in the photos, in particular, it’s actually pretty small for a sunglass.  A 53 eye size is pretty small, especially for my face, as a rule.  But as you can see here, it fits me pretty well.  This is all because there is a fair bit of frame outside of the lenses before reaching the temples, to go back towards my ears.

In addition, my nose is fairly small, and I often need as small as a 16 bridge size.  This frame is a 20 and fits almost perfectly.  Again, the frame plastic is quite thick in the bridge which allows a smaller nose to still fit with a larger number (20 in this case).

Do you still have any questions?  Please ask in the comments section below.