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All About Frame Measurements

frame measurements

All About Frame Measurements

Picking out new frames can be a difficult decision for any glasses wearer. It’s a choice that sits on the face, sometimes for years. That’s why it is so important to pick a frame that fits well, looks good, and makes you feel confident and empowered to wear glasses every single day.

This post will help give you the tools to understand the different measurements on a glasses frame. This is so when you go to pick out your next frame, you have the knowledge to make an informed decision.

When looking for frames, you may have noticed that optical frames have three numbers on the inside of the temple, or sometimes on the bridge. These numbers are the eye size, bridge width, and temple length. These are all important for finding a frame that will fit you correctly.

Eye Size: 

The eye size, the ‘A’ measurement, or the lens width measures the width of the lens on the frame. Finding the right size here ensures that your eyes are centered in the frame. It also helps to frame the face, giving you the best look possible.


The bridge measures the distance between the two lenses. If the bridge is too small, it can pinch and cause discomfort for the wearer. If the bridge is too big, the glasses won’t sit right and can slide down the nose. This is most important when the frame doesn’t have nosepads and the bridge needs to fit perfectly.

Temple Length: 

The temple length is the length of the two arms that hold your frames behind your ears. You want a frame that is long enough to have a good arch over your ear, but not too long that it sticks out far into your hair. This piece is essential for securing the glasses on your head, so proper temple length is a must!

B Measurement:

An additional measurement that is often overlooked, the ‘B’ measurement, is the depth of the frame. This is important for progressive wearers. If the B measurement is too big, a progressive wearer may have trouble accessing the reading part of their glasses. If it’s too short it can cut into the reading portion of the lens, and make it difficult for the wearer to read.  For higher prescriptions, it can make the lens appear thicker.

Other measurements you may have heard before include the PD, seg height, and optical center. These measurements all have to do with the actual lens inside your glasses, so while you don’t need them to pick out a great frame, it is important to understand them so your completed pair works perfectly for you.

Pupillary Distance:

The pupillary distance, or PD, is the distance between your pupils. This is an important measurement to make sure the prescription is horizontally centered.

Optical Center:

The optical center, or OC is the vertical measurement for single vision glasses that centers the prescription vertically in the lens. This measures the distance from the pupil to the bottom of the frame.

Segment Height:

The segment height, or seg height, is similar to OC but used for progressive lenses or bifocals. This is the distance from the bottom of the lens to where the reading prescription starts.

As you can see, accurate measurements are very important to make sure the prescription is centered in front of the pupil so the vision is clear.  While it is possible to take these measurements on your own, for best results you should see an optician to assist you. They will make sure your glasses look great and fit properly.

Start taking care of your eye health today!