Glasses Frames -Our Frame Sizing Information

Steve Mower - July 2021

frametoobig.jpg < Not even close.

Glasses Frames- How to choose the right size eye glass frames.

When shopping for glasses frames, whether for prescription or non prescription, it is really important that you choose one that fits properly. Ideally, the glasses frames should be wide enough so that the temples, or 'arms', go straight back to your ears without putting pressure on the side of your head. That pressure can result in headaches and unsightly dents in your head, and nobody that I know wants dents in their head. Glasses frames should also not be so wide that they slide down your nose all the time.

2. Optical Frame Size and Bridge Width - This is the way prescription eyeglass frames are sized. All prescription frames are sized based on 3 measurements, in millimeters-

  1. The length or width horizontally, of one lens in millimeters (mm).
  2. The length or width of the bridge, again, in millimeters (mm).
  3. The length of the temples in millimeters (mm).
  4. The lens height in millimeters (mm).

Example of eyeglass frame measurements

A Chart-

ss124 (46K)

So a typical size might look like "53-18-138" (lens-bridge-temple usually printed on the inside of the temple) This information is important to opticians but because of the widely different frame styles available, these numbers are fairly meaningless to most eyeglass shoppers. However, knowing what these numbers represent can help you to understand exactly what you are getting, especially in combination with the frame fit. When available we also provide the lens height. The height, or depth as you may, is the mm measurement from top to bottom of the lens and is not critical for sizing but is important when buying progressive lenses.

Conversion to inches. One millimeter is 1/37th of an inch. You can roughly calculate the total width of your current eyeglasses in inches. See above image.

First determine the total width in millimeters... Eye Size x 2 + Bridge Width +~ 8-10mm end-piece extension. (Most frames have temples that extend away from the frame front. It varies.)

Frame "Fit" - We group our eyeglass frames into Frame-Fit categories. A Medium Fit fits medium width faces. 

Small    44-47mm
Small Medium   47-50mm
Medium  .......  49-52mm
Medium Large   52-54mm
Large    54-56mm
Extra Large   56mm and up

*This is a rough guide. The thing is, is that the extension of the temples and the bridge width can make a big difference in the "fit". A 46-22 can fit the same as a 48-18. Both are 114mm across.


  1. You can filter your search on our site by Frame Fit, Bridge Width, and Temple Length. Choose a frame fit/eye-size and then choose a bridge width and then temple length.
  2. Frames with adjustable nose pads provide the freedom to have the pads adjusted to fit, whereas frames without adjustable nose pads will fit or not.
  3. You do not have to be accurate to the millimeter. 1 millimeter difference either way in the eye-size, bridge, and temple isn't enough of a difference.
  4. Quality eyeglass frames are adjustable. Opticians can fit the frame to your face properly.   
  5. The best way to determine the frame size you need is to pick a frame that you own, or have tried on that is comfortable for you. Read the numbers on the inside of the temples and search accordingly.

Here are 2 handy conversion calculators...

Millimeters to inches-

Convert mm to in


And inches to millimeters-

in to mm calculator




Steve Mower is a licensed Optician and creator of Mojo BluBlock Tints. Steve has over 30 years experience in the optical field. He has been a optical retail manager and has consulted on progressive lens development. Steve has been offering unique reading glasses solutions on-line since 2010.

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