How to Find Your Frame Size Using Your Current Glasses

If you already own a pair of glasses that fits well, you're holding the best sizing tool there is. Most frames have their measurements printed right on them. Once you know how to read those numbers, buying your next pair online gets a lot less guesswork.

As a board-certified optician, I've fit and made thousands of pairs of glasses. Here's how to find your numbers, what each one means, and how closely your new frames need to match.

Where to find the numbers

Take off your glasses and look at the inside of the temple arms. On most frames you'll see a string of three numbers, something like this:

52 – 18 – 140

On some frames the numbers sit on the inside of the bridge or behind a nose pad instead. One arm often holds the size, and the other holds the model name and color code. All three numbers are in millimeters.

What each number means

Number	Example	What it measures	Typical range
Lens width (eye size)	52	Width of one lens at its widest point, side to side	40–60 mm
Bridge width	18	Gap between the two lenses, where the frame sits on your nose	14–24 mm
Temple length	140	Length of the arm, from the hinge to the tip behind your ear	135–155 mm

Lens width has the biggest effect on how wide the frame looks and feels on your face. Together with the bridge, it sets the frame's overall width.

Bridge width controls where the frame rests on your nose. Too narrow and it pinches or sits high; too wide and the frame slides down.

Temple length decides how well the arms hook behind your ears. It's the most forgiving of the three.

You may also see a lens height listed on product pages. It measures the lens from top to bottom. It's rarely printed on the frame, but it matters if you wear progressive lenses (more on that below).

How closely your new frames need to match

You don't need an exact match. Frames that land within these ranges of your current pair will usually fit about the same:

Measurement	Stay within	Why
Lens width	±3 mm	Small changes noticeably widen or narrow the frame
Bridge width	±2 mm	Nose fit is sensitive, especially on frames without adjustable nose pads
Temple length	±5 mm	Arms can be adjusted, and most fall between 140 and 145 mm

If you have to compromise, prioritize lens width and bridge first. A slightly different temple length is the easiest thing to live with.

Keep in mind that frame shape changes the feel too. A 52 mm round lens and a 52 mm rectangular lens won't look identical on your face, even with the same numbers. If you want to see how a new style looks before you buy, the "Try on" button on our product pages lets you preview frames on your own face.

What if the numbers have worn off?

It happens, especially on older or well-loved frames. You can measure them yourself with a ruler marked in millimeters:

1.     Lens width: measure one lens straight across at its widest point, edge to edge.

2.     Bridge width: measure the narrowest gap between the two lenses.

3.     Temple length: measure the arm from the hinge to the very tip, following the bend behind the ear.

Home measurements can be off by a millimeter or two, so treat them as a close estimate rather than an exact number.

First, make sure your current pair actually fits

Your old frames are only a good template if they fit well. Put them on and check:

•      Your eyes sit roughly in the center of each lens, side to side.

•      The frame doesn't press on your temples or leave red marks on your nose.

•      The glasses stay put when you look down, without constant pushing back up.

•      The arms run fairly straight back to your ears instead of bowing outward.

If something feels off, adjust your target numbers in that direction. For example, if your current pair feels tight at the sides, look for a lens width 1–2 mm wider.

A note for progressive lens wearers

Progressive lenses need enough vertical room to fit distance, intermediate and reading zones. As a general rule, look for a lens height of at the least 33mm. Very slim frames can squeeze the reading area and make progressives harder to adapt to.

Ready to find your next pair?

With your three numbers in hand, browsing for frames online gets much simpler. At Peek Eyewear every product page lists the frame's measurements, so you can compare them side by side with your current pair. We also offer a virtual try on feature so you can see how your next pair of eyeglasses will look on your face. Grab your current glasses, check the numbers, and shop our frames.