Shopping for glasses online can save you money, but the biggest fear most people have is simple: "What if they don't fit?" Unlike buying frames in a store where you can try them on, ordering glasses online requires you to trust measurements you may not fully understand. One wrong number and you could end up with frames that pinch your temples, slide down your nose, or look comically oversized on your face.
If you have ever wondered how to choose the right frame size when buying glasses online, you are not alone. Many shoppers struggle with confusion around lens width, bridge width, temple length, and how these measurements relate to their actual face. In this guide, we will walk through the basics of online glasses sizing, common mistakes to avoid, and how to make sure your new frames fit comfortably from the moment they arrive.
When people shop for glasses in person, they rarely think about specific measurements. They simply try on several pairs and pick the one that feels right. But when you order online, you lose that tactile feedback. You cannot feel whether the temples are too tight or whether the bridge sits comfortably on your nose. That is why understanding frame size becomes critical.
A frame that is too wide will constantly slip down, no matter how much you adjust the nose pads. A frame that is too narrow can cause pressure headaches and leave red marks on your temples. Even if the lenses are perfectly matched to your prescription, poor frame fit makes glasses uncomfortable to wear all day. This is especially true if you are ordering reading glasses, which you may wear for hours at a time while working or reading.
Most glasses have three numbers printed on the inside of the temple arm, usually separated by small squares or dashes. For example, you might see something like 52 □ 18 – 140. These numbers tell you the frame size in millimeters:
If you already own a pair of glasses that fit well, check the inside of the temple for these numbers. Use them as your baseline when shopping online. If your current frames are marked 50-17-135 and feel comfortable, look for new frames in a similar range. If you are buying glasses for the first time, you will need to estimate based on your face width and features.
If you do not have old glasses to reference, you can measure your face at home with a ruler or a flexible measuring tape. Here is how:
For a detailed breakdown of how to match frame size to your face shape and width, check out a complete size chart guide for first-time buyers.
Even with measurements in hand, many people still make avoidable errors when ordering glasses online. Here are the most common pitfalls: