You may notice numbers such as “47-19-140” in the temple of glasses frames. But did you know these numbers actually describe the frame size? Glasses manufacturers typically use the same format to detail sizes. And it’s easy to find the correct frame size for your face type. Simply measure your face or check your current glasses to find the ideal size. Opticians and optometrists also rely on these numbers to determine the best fit.
We’ve put together this guide to help you understand exactly what these numbers mean and how to read them correctly.
Table of Contents
Reading Frame Size and Dimensions
Before we review what these numbers mean, let’s first understand how to read frame measurements. You read the numbers from left to the right in the following order:
- 1st Number – Is the lens width
- 2nd Number – Is the bridge width
- 3rd Number – Is the temple length
Finally, these measurements are expressed in millimeters (mm). You can see this illustrated below with a pair of Oakley sunglasses.
Eye Size
The first number is the eye size, also known as the lens width. It shows the horizontal width of the lens at its widest point. For example, most glasses have a lens width between 44 mm and 62 mm. The eye size is measured for each lens.
The eye size is essential for ensuring the frames fit your face since most manufacturers use this measurement to determine the frame size. As a general rule of thumb:
- Small frames have an eye size between 49mm and 54mm
- Regular/medium frames have an eye size between 55mm and 57mm
- Large frames have an eye size between 58mm and 63mm
You can also measure your face and determine the right size glasses. Simply use a ruler to measure your face size from temple to temple. Then, use this measurement to find the perfect eyeglass frame size.
For example, a face size of between 4.5 – 5.1 inches requires a small frame. Regular frames are good for a face size between 5.25 and 5.5 inches. Lastly, a large frame fits a face size between 5.75 and 6.25 inches.
Bridge Size
The second number is the bridge size. It indicates the width of the bridge. The bridge is that part of the glasses that sits on your nose. Again, this is typically a two-digit number. And most eyewear bridge sizes range between 14 and 24 mm.
Your face size largely determines the ideal bridge size. For example, people with close-set eyes or narrow bridges may want to go for a smaller bridge size. Bridge sizes between 15mm and 18mm are ideal in this case. Conversely, people with wide-set eyes or wider bridges might want a higher bridge width. The optimal range is between 18mm and 22mm for people who fall in this category.
The bridge size also plays a vital role in comfort. An oversize bridge will cause your glasses to slide down your face. You also won’t be able to shake your head from side to side or bend over without the frame sliding off your face. Similarly, a bridge that’s too small will pinch. The frames will also sit too high on your nose, which affects the pupillary distance.
The pupillary distance is used to determine how you see through the lenses. Your pupils need to be in the correct position behind the lens to see clearly.
Temple Length
The temple length is typically shown as three numbers, such as 120mm or 145mm. This number indicates the length of the frame arm from the hinge to the end tip. The length varies between 120mm to 150mm for most glasses.
The temple length ensures the glasses fit correctly over your ears. However, the wrong size may angle over the ear and slip from your face. Also, glasses with the wrong temple size slip more often when you’re sweaty.
Alternatively, you can purchase glasses or sunglasses with adjustable temples for a guaranteed fit.
Side Note: About Frame Height
There is a fourth number worth mentioning. This is the lens height which is important in some instances. For example, bifocal and progressive lenses have multiple focus zones. So you’ll need to make sure you have enough vertical space to accommodate the prescription. Most multifocal glasses have a lens height of at least 30 mm.
However, most manufacturers do not indicate the lens height on the frame. You may also not find this information on the vendor’s website. In this case, make sure that the lens is specifically designed for multifocal prescriptions.
Alternatively, contact the vendor to find out if the lenses have sufficient height for your prescription.
Model Numbers and Serial Numbers
It’s worth noting that these numbers aren’t only printed on the inside temples of the glasses frame. Some manufacturers print these numbers inside the nosepiece or the back of the bridge.
You might see other numbers on the inside of the frame. These typically denote the frame model number or serial numbers. But, again, it’s easy to distinguish these numbers from the frame measurements we discussed.
Model numbers and serial numbers typically have a more extended sequence and include a mix of letters and numbers. So, for example, you may see something like OX1062-0552 appear before or after the frame size.
Many glasses manufacturers print the model number or serial number on one of the temples and the frame size on the other. This design makes it easier to distinguish between the two numbers.
Finally, some manufacturers also print a code to reference the frame style, material, or color.
Do All Eyeglasses and Sunglasses have Numbers on the Frame?
Besides the lens prescription, optometrists need a way to determine if the eyewear is right for you. So, most eyeglasses and sunglasses have numbers on the frame. At least, this is the case with big-name brands.
However, not all prescription glasses and sunglasses have these key measurements. In this case, finding the right sunglasses size can be challenging when shopping online.
Looking for more?
Want more insights and guides? Or have a question? Check out the links below or let us know in the comments section:
