Eyeglass Frame Numbers: Understanding Your Glasses Size

Where to find the numbers on eyeglass frames?

Before you can decipher them, you have to find them! Take your glasses and look closely at the inside of both arms (the stems that rest on your ears). In most cases, the sequence of numbers is found on the inner side of the left arm.

You will usually see a series of three numbers, separated by a small square or a dash, which looks like this: 52 [] 18 - 145.

Sometimes, this information might be discreetly engraved on the bridge, the part that connects the two lenses and rests on your nose. If the numbers have faded over time, don't worry, a qualified optician can measure your frame in a few seconds.

The 3 Key Dimensions: Decoding Your Frame's Numbers

The series of three numbers is the most important. It corresponds to the fundamental dimensions of your frame, always expressed in millimeters (mm). Let's understand what each number means using our example: 52 [] 18 - 145.

The First Number: Lens Width (the Calibre)

The first number, here 52, represents the horizontal width of one lens. In optics, this is known as the "calibre". It measures the lens at its widest point.

• Why is this important? This measurement directly influences the overall size of the frame and how it harmonizes with your face. Someone with a wider face and widely spaced eyes will be more comfortable with a larger calibre (for example, 54 or 55). Conversely, a narrow face will be better complemented by a smaller calibre (for example, 48 or 50). This isn't an absolute rule, but it's an excellent starting point for both aesthetics and comfort.

The Second Number: Bridge Width

The second number, here 18, indicates the width of the bridge. This is the distance separating the two lenses. In other words, it's the width of the part of the frame that will rest on the bridge of your nose.

• Why is this important? This is a crucial element for comfort!
  • If the bridge is too narrow: The glasses will sit too high on your face, and the nose pads (the small plastic supports) might pinch your nose.
  • If the bridge is too wide: The glasses will constantly slide down your nose, forcing you to push them up repeatedly. A poor fit can also affect your field of vision. Finding the right bridge width is therefore essential for your glasses to stay securely in place all day.

The Third Number: Temple Length

The third and final number, here 145, corresponds to the total length of one arm, from the hinge to its tip.

• Why is this important? This length determines how the frame will hook and sit securely behind your ears.
  • If the arms are too short: They won't be able to curve properly behind the ear. The glasses will be unstable and may fall off when you look down.
  • If the arms are too long: The frame will be loose and tend to slide forward.

The most common temple lengths for adults are 135, 140, and 145 mm.

What Do the Other Letters and Symbols Mean?

In addition to the three-number sequence, you might find other markings on the frame. They provide additional information about the model.

• The Model Name: Often, a name or a code (e.g., "LP 2045" or "Amara") is written before the number sequence. This is the manufacturer's reference, useful if you want to find the same model again.
• The Colour Code: You might also see a code like "C01" or "BLK". This is simply the reference for the colour of your frame (e.g., "C01" for the first colour in the catalogue, "BLK" for black).
• The "CE" Mark: These two letters stand for "Conformité Européenne" (European Conformity). Even for glasses sold in Africa, this mark is a sign of quality. It indicates that the frame meets certain safety and durability standards, notably that it does not contain materials harmful to the skin.

Why Is It So Useful to Understand These Eyeglass Frame Numbers?

Now that you know how to read your frame's dimensions, you hold valuable power for your visual health and comfort.

To Choose a New Frame with Confidence

If your current glasses fit you perfectly, take note of their dimensions! These numbers (calibre, bridge, temples) become your personal guide. When you look for a new pair, whether in a store or online, you can compare new frames to your ideal measurements. It doesn't replace trying them on, but it allows you to quickly filter out models that are most likely to suit you.

To Make Replacing Your Lenses Easier

Imagine your prescription changes, but you love your current frame. You can absolutely just replace the lenses. The dimensions engraved on the frame are essential for the optician. Whether you are in Ivory Coast, Burkina Faso, Uganda, or any of the many countries where Lapaire operates, our opticians will use this information to cut and fit your new lenses into your favourite frame with perfect precision.

My Numbers Are Faded or Unreadable, What Should I Do?

Over time, due to sweat and friction, it's common for the markings on frames to fade and disappear. Don't worry, this is not a problem!

The best solution is to visit an optical centre. An optician has specific measuring tools (like an optician's ruler) to quickly find the exact dimensions of your frame: lens width, bridge size, and temple length. This is also the perfect opportunity to have the general fit of your glasses checked. At Lapaire, we are always happy to help and even offer a free eye test during your visit. It’s an excellent opportunity to kill two birds with one stone: find out your frame size and check if your prescription is still up-to-date.

Understanding the numbers on your eyeglass frames makes you more independent and better informed. You now know that the "calibre - bridge - temple" sequence is the key to optimal comfort and a good fit. This knowledge will help you communicate more easily with your optician and make informed choices for your future eyewear.

Remember that these measurements are an excellent guide, but nothing replaces the advice of a professional. For a perfect fit and a complete check of your vision, visit one of our Lapaire branches. Our teams are there to offer you a free eye test and help you find the glasses that are perfect for you.

This article is for informational purposes. For a personalized diagnosis, consult a Lapaire optician.