Sizing & Fit
How to Measure Glasses for the Perfect Case Fit
Measuring prevents the two most common mistakes: buying a case that will not close or one so large that the glasses rattle.
Record outside width, maximum height and folded depth in millimeters. Compare them with usable interior measurements, not the case’s outer size.
Measure the actual folded pair
With temples folded normally, measure the widest outside point, tallest point, and deepest folded area. Millimeters make product comparisons easier.
Separate frame numbers from case measurements
Printed frame numbers usually show lens width, bridge width, and temple length—not total case dimensions—so measure the actual pair.
Treat resistance as a failed fit
Never force a lid. Pressure at corners, hinges, or nose pads means the interior is too small.
A ruler method you can repeat
Place a clean ruler beside the glasses on a stable surface. Keep the pair in its normal folded shape; do not press curved frames flat. Read the distance between the furthest outer points across the front. For height, use the tallest point including decorative corners. For depth, include the folded temples and any projecting nose pads.
If holding the ruler makes the pair move, place two straight objects just outside opposite edges and measure the gap between them. Keep those objects away from the lenses. A household ruler is good for comparison, but small measurement uncertainty means a listed exact match is not enough to establish fit.
Copy this measurement worksheet
The example is invented to show the method, not a recommended universal size.
| Measurement | Your pair | Example |
|---|---|---|
| Maximum outside width | _____ mm | 145 mm |
| Maximum outside height | _____ mm | 48 mm |
| Folded depth | _____ mm | 35 mm |
| Case usable interior | _____ × _____ × _____ mm | Must exceed each pair measurement |
Why there is no universal clearance rule
A rounded case loses room at its corners, and a zipper or lining can take up space. Two cases with the same maximum interior numbers may fit differently. Ask for the narrowest usable width and depth if the shell is tapered. If you can try the case, its lid should meet naturally without any part of the frame bearing the closing force.
Questions about sizing & fit
Can I use temple length as the case length?
No. Temple length describes an unfolded arm, while case fit concerns the whole folded pair. The arm’s shape and where it rests also affect depth.
Should I use inches or millimeters?
Either works if you convert consistently. Millimeters usually make comparisons simpler; one inch equals 25.4 millimeters.
Use this guide to evaluate fit and specifications. This is a retailer link, not a claim that we have tested every product.
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