Glasses Case Size Finder: Turn Your Frame Numbers Into Case Dimensions
The three numbers printed inside your glasses' temple arm are enough to estimate what size case you need. Enter them below, choose how curved or chunky your frames are, and get a recommended interior size in millimeters and inches.
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Buying a case online is easy until it arrives and will not close over your glasses. Most of those mistakes come down to size. This tool uses the measurements already printed on your frames to estimate the interior dimensions your case needs, then compares them with the published interior sizes of a few widely sold cases.
Find your frame numbers
Look on the inside of one temple arm (the part that goes over your ear), or sometimes on the bridge. You will see three numbers, often like 52-18-145 or 52□18 145:
- Lens width (first number), in millimeters: usually 40 to 62.
- Bridge width (second number): usually 14 to 24.
- Temple length (third number): usually 120 to 155.
Some frames also list a lens height, and some product pages list the full frame width. Our frame size numbers guide explains each one in detail.
The case size finder
The result is an estimate. Frames with the same numbers can differ in shape, curve and hinge design. If you have your glasses handy, measuring them folded (method below) is always the most accurate check.
How the estimate works
We wanted the method to be transparent, so here it is.
- Front width. The frame's front is roughly two lens widths plus the bridge, plus a few millimeters of end pieces on each side: 2 × lens + bridge + 8 mm. If you enter a total frame width from a product page, the tool uses that instead.
- Folded length. When the temples fold, they lie behind the lenses. On frames with a narrow front and long temples, the folded temples can stick out past the hinge, so the tool takes the larger of the front width and the temple length minus about 25 mm (the curved ear piece bends back).
- Height. If you enter a lens height, the tool adds 8 mm for the frame rim. If not, it estimates lens height as about 78% of lens width, which is typical for everyday frames, and marks the result as estimated.
- Depth. Depth depends mostly on how curved or chunky the frame is, so the style menu sets a typical folded depth: about 28 mm for thin and flat frames, 35 mm for typical acetate, 44 mm for chunky or curved frames and sunglasses, and 52 mm for wraparound sport frames. These are general guidance figures, not measurements of your frame.
- Room to close. The minimum recommended interior adds 6 mm to the length and 4 mm to the height and depth, so the case closes without pressing on the lenses. A "comfortable" size adds a little more.
- Comparison. Finally, the tool compares your result with the interior dimensions published in the listings of four widely sold cases, as shown on October 26, 2026: RayLove hard shell (153 × 53 × 33 mm), Hifot aluminium (152 × 57 × 26 mm), a slim magnetic case sold by Payne Glasses (160 × 60 × 30 mm) and the NoCry zip case (163 × 76 × 53 mm). These are examples, not recommendations from testing.
Worked examples
To show how the numbers play out, here are five example frames run through the same method. They are illustrations, not specific products.
| Frame numbers and style | Estimated folded size | Minimum case interior | What that suggests |
|---|---|---|---|
| 44-20-145, thin metal readers | 120 × 42 × 28 mm (temples set the length) | 126 × 46 × 32 mm | Almost any standard or slim case |
| 48-20-140, thin metal | 124 × 45 × 28 mm | 130 × 49 × 32 mm | Slim hard or aluminium case |
| 52-18-145, typical acetate | 132 × 49 × 35 mm | 138 × 53 × 39 mm | Standard hard case with some depth, or a zip case |
| 55-18-145, chunky or sunglasses | 136 × 51 × 44 mm | 142 × 55 × 48 mm | Semi-rigid zip case or a large case |
| 62-15-130, wraparound sport | 147 × 56 × 52 mm | 153 × 60 × 56 mm | Large or sport-specific EVA case |
Two patterns stand out. First, depth rules out slim cases more often than length does: a typical acetate frame is short enough for a slim case but too deep for one. Second, on small frames with long temples, the folded arms can be the longest part, which is why the first example's length comes from the temple rather than the front.
Measure your glasses by hand
If the numbers have worn off, or you want to confirm the estimate:
- Fold the glasses and lay them on a table.
- Length: measure the widest point from hinge to hinge (or to any temple tip that sticks out).
- Height: measure the tallest point of the frame front.
- Depth: with the glasses lying lens-down, measure from the table to the highest point.
- Add room: at least 6 mm to the length and 4 mm to the height and depth.
Compare those numbers with the interior dimensions a case listing gives. If a listing only gives outside dimensions, subtract a few millimeters for the walls, or more for thick hard shells. Our guide to choosing a case has diagrams.
What the size categories mean
| Result | Typical case to look for |
|---|---|
| Interior up to about 155 × 55 × 33 mm | Standard or slim hard clamshell; see slim cases |
| Up to about 165 × 62 × 40 mm | Standard-to-large hard case or a semi-rigid zip case |
| Up to about 170 × 78 × 55 mm | Large semi-rigid zip case; see cases for oversized frames |
| Larger, or a strong wrap | Extra-large or sport-specific EVA case; see sports glasses cases |
Frequently asked questions
Where are the size numbers on my glasses?
Usually on the inside of one temple arm, sometimes on the inside of the bridge. They are printed in millimeters, for example 52-18-145.
Does temple length affect case size?
Sometimes. On narrow frames with long temples, the folded arms can extend beyond the hinges, so the case needs to be longer than the frame front.
Why does the tool ask about frame style?
Depth depends mainly on how curved and thick the frame is, and that is not captured by the printed numbers. The style setting applies typical depth values.
Is the estimate guaranteed to fit?
No. It is an estimate based on typical frame proportions. Measuring your folded glasses is the most reliable check, and allowing a few extra millimeters is always safer than a tight fit.
Bottom line
Your frame's printed numbers are a quick way to narrow down case size: enter them above, pick your frame style, and look for a case whose published interior meets or beats the recommended size. When the glasses are in hand, a ruler gives the final answer.