This guide explains how to choose the ideal sunglasses or optical glasses, either by matching the size of an existing pair or by utilizing a credit card as a measurement tool.


Most glasses typically have the size measurements stamped or printed on the inside of the left temple (the arm piece that goes behind your ear). Some manufacturers stamp the first two numbers (Lens Width and Bridge Width) on the bridge (the part that sits on your nose). The measurements consist of a series of numbers such as: 58▢15-130. The size measurements are for Lens Width, Bridge Width and Temple Length in that order. These measurements are in millimeters.

Eyewear Size Guide

Using your existing glasses, simply add the Lens Width and Bridge Width. In the example we have here, we would add 58 and 15 to get 73, which is a Medium size according to the chart below. Now you can use the chart below to determine your ideal fit after you've added the two numbers. It is important to note that you don't need to be exact. Your new pair should be within 1-3mm of your current lens width, 1-3mm of the bridge width and 4-6mm of the temple length. About 90% of people fall into the Medium size category. When shopping for your ideal glasses, we display both the frame measurements and the size, such as 58-15-130 (Medium).

Lens Width + Bridge Width
Small 71mm or less
Medium 72mm - 75mm
Large 76mm or more


If you do not have an existing pair handy, grab a credit card instead. Stand in front of a mirror or web cam, place one edge of the card at the exact center of your nose and observe the place where the other edge ends. Take a look at the illustration image and chart below to easily determine your size.

Trovelle Frame Size Measurement
Small Card extends beyond the end of your eye.
Medium Card ends at the end of your eye.
Large Card does not even reach the end of your eye.


Bifocals and progressive frames: A fourth number if available on your glasses is the lens vertical height. This number is not commonly notated by eyewear makers. The number is important when shopping for bifocals or progressive prescription frames, since they do require a minimum lens height. The minimum fitting height for progressive lenses is 28-30mm.

Helpful tips: You can search for eyewear using your exact measurements. For example, you can type 55-17-135 in the search box to see exact matches. You can also use the filter tool located in search results and collection pages to narrow down your selection based on brand, frame and lens colors, size, frame measurements and price.

Need help? Get in touch with us and we will do our best to help you choose the right fit that best suits your style.