Getting a pair of glasses online that fits perfectly sometimes feels like finding buried treasure. However, if you know how to find your glasses frame size, it should be super simple. Measuring your face or a pair of glasses you own helps you find your exact fit so you can choose comfortable and stylish eyewear.

Learning what methods to use to measure your glasses prepares you to take precise measurements and find the frames that are right for you. You’ll learn all you need to know about how to measure glasses in this guide, plus some tips on finding the perfect glasses next time you shop.

How to Measure Glasses Size

When trying to find your best glasses fit, a great place to start is with the measurements of a pair you already own. You can measure a pair of eyeglasses or sunglasses — just remember that style impacts size. If you use sunglasses, it could affect your measurements because they tend to be larger than eyeglasses.

Look inside the arms of your pair of glasses and locate three numbers inside the temple. These three numbers relate to the lens width, bridge width and arm length. You may also see a fourth number corresponding to lens height. All of these measurements are noted in millimeters.

Check out these common glasses measurements and learn how to measure your glasses frames:

Lens Width

The lens width of your glasses is the first number you’ll see inside your glasses. Lens width refers to the horizontal width of your lenses at their widest part. This number ranges between 31 and 60 millimeters.

If your glasses don’t have this number or you want to measure the frames to be sure, take these steps:

  • Hold a straight ruler against your lens at its widest point.
  • Measure horizontally.
  • Convert the inches or centimeters to millimeters.

Bridge Width

The bridge width of your glasses is the distance between the lenses, the space where your glasses will fit against your nose. This measurement is the second number you’ll see inside your glasses temple and can range from 12 to 31 millimeters.

Here’s how to find the bridge width of your glasses:

  • Place the ruler across the bridge between the two lenses.
  • Measure horizontally from one edge of a lens to another, including the frame in the measurement.
  • Convert your measurement to millimeters.

Arm Length

The last number in a typical sequence indicates the arm length, also called temple length, which refers to the measurement from the screw on the hinge to the arm’s tip. The arm length measurement should include the arm’s bend that sits over your ear. This measurement is between 115 to 155 millimeters, with typical lengths including 130, 140 and 145 millimeters.

Here’s how you measure glasses arm length:

  • Hold the ruler at the hinge of one arm.
  • Measure from the screw to the bend.
  • Measure again from the bend in the arm to the tip.
  • Add the measurements together and convert the total to millimeters.

Lens Height

Your glasses may include lens height, which is the vertical measurement of each lens at its tallest point. This measurement doesn’t include your glasses frame sticking above and below the lens. An accurate lens height is crucial if your lenses are bifocals or progressive.

Follow these steps to measure the lens height on your glasses:

  • Hold the ruler vertically against one lens at its tallest point.
  • Convert the measurement to millimeters.

How to Measure Your Face for Glasses

Whether it’s your first time buying glasses or you don’t have a pair of glasses that fits, you can also measure your face size to find your perfect glasses fit. Here are the steps for measuring your face for glasses: 

1. Pick a Measuring Tool

You can use multiple measuring tools to measure your face for glasses:

  • The ruler method: Rulers are easy to use and provide accurate measurements if you read them correctly.
  • The tape measure method: A tape measure will be just as accurate as a straight ruler. Be careful not to bend the tape measure, or you could distort the measurement.
  • The credit card method: This method might be applicable in a pinch, but it’s the least accurate method because it only gives an estimated glasses size rather than precise measurements.

2. Calculate Your Ideal Bridge Width Measurement

Discovering how to measure the bridge for eyeglasses requires considering your nose shape and its position on your face. Stand in front of a mirror for the best accuracy or take a side profile selfie to look closer.

If your nose bridge is narrow or begins level with or below your pupils, your ideal glasses bridge size is a lower number. You might look for frames with a bridge width between 14 and 18 millimeters. A high or wide bridge requires a larger bridge width for the best fit. Frames with a bridge width between 19 and 22 millimeters will be the best choice.

3. Measure Your Lens Width

You’ll have to measure your total face width to find your ideal lens width. Hold the ruler or tape measure across your face right below eye level. Measure horizontally from your left to your right temple. This number is the total width of your ideal frame size.

To calculate individual lens width, subtract your bridge width measurement from your face width. Then, divide that number in half to find the best approximate lens width for your face.

4. Find Your Glasses Arm Length

The final measurement to calculate is the arm length. You can use your face width measurement to determine the best length for the arms of your glasses.

  • A face width of around 129 millimeters or narrower works best with an arm length between 130 and 140 millimeters.
  • A face width between 130 and 139 millimeters is ideal for glasses arms between 140 and 145 millimeters.
  • A face width that’s 140 millimeters or wider works best with an arm length of 145 millimeters or more.

5. Determine Your Frame Size

Once you have your face measurements, you can find the right frame size. You can use this glasses size calculator to determine the size of your glasses frames based on the measurements you took above:

  • Small: If your face width is less than 129 millimeters, your ideal lens width is likely around 50 millimeters or less. Your glasses arm length should be between 130 and 140 millimeters. A small bridge width is between 14 and 16 millimeters.
  • Medium: If your face width is between 130 and 139 millimeters, your ideal lens width is likely between 51 and 55 millimeters. Your glasses arm length should be between 140 and 145 millimeters. A medium bridge width is between 17 and 19 millimeters.
  • Large: If your face width is over 140 millimeters, your ideal lens width is likely 56 millimeters or more. Your glasses arm length should be 150 millimeters or above. A large bridge width is between 20 and 23 millimeters.

How to Find Your Glasses Frame Size

With your glasses size and face measurements in mind, it’s time to pick your new frames. Finding the correct fit is essential for choosing frames you can wear confidently and comfortably all day long. Style is another factor that impacts how glasses complement your features and face size.

Here are a few tips for finding your perfect glasses frames:

1. Select the Right Frame Width

Overall frame width refers to the measurement of a pair of frames from one arm hinge to another. Glasses with a broader frame width than your face could make your face look larger. Choosing glasses with a narrower frame width than your face could have a shrinking effect.

The best frame width is usually slightly wider than your face, including any designs that stick out from the frames. Your frames should also leave about a finger’s width between the temple and your face. Any wider, and the frames are likely too large.

2. Find the Perfect Lens Height and Width

Lens size is typically measured in width, though height might also be a factor in your decision. Remember that small lenses have a width of 50 millimeters or less, medium-sized lenses are between 51 and 55 millimeters and large lenses are wider than 55 millimeters.

The right lens size for you is whatever size positions your eyes directly in the middle of the lenses. Larger lenses could make your eyes appear closer together, while smaller lenses could give your eyes a wide-set look. When you smile, the glasses should continue resting on your nose rather than get bumped by your cheeks.

3. Pick the Right Bridge Width

Glasses bridge width is crucial for your frames’ comfort. The perfect bridge width should sit comfortably flat against the bridge of your nose. Pick a smaller bridge width if you have a narrow nose or closer-set eyes. If you have a broad nose bridge or wide-set eyes, frames with a larger bridge width will work best.

4. Understand Arm Length

Arm length doesn’t have to be as precise as bridge width and lens width for a comfortable fit. Still, the arms of your frames should fit correctly along the contour of your ears. If the arms are too short, they may push your glasses too far down your face.

5. Consider Materials and How They Fit

When picking your frames, consider how different materials could affect your glasses’ wear. For example, having the correct bridge width is more critical with plastic or acetate frames than with metal glasses — the wrong fit could leave your frames sliding on your nose. Metal glasses come with adjustable nose pads that give you the proper fit.

If you’re getting new plastic frames after wearing plastic frames that fit well, try to use the same bridge measurement. If you’re going from plastic to metal frames, your bridge width can vary by 2 to 3 millimeters and still fit correctly.

Glasses Measurements FAQs

If you’re interested in learning more about glasses measurements and how to find the right fit, these frequently asked questions can get you the answers you need:

How Do You Know if Your Glasses Don’t Fit Your Face?

Any signs of looseness, tightness or constant sliding indicate that your frames don’t fit your face correctly. If your frames are too wide, the arms might feel loose and won’t sit snugly over your ears. Your glasses might slide down your face if the bridge is too broad.

How Do You Determine Your Face Shape?

You can figure out your face shape by looking in the mirror and analyzing the dimensions of your face. Many people consider their face shape when looking for frames that complement their features. Your decision should ultimately come down to which frames you like best, no matter your face shape.  

Consider a few common face shapes:

  • Oval: An oval face has wider cheekbones and a narrower jaw and forehead. 
  • Square: If your face has an even width at the forehead, cheekbones and chin, you might have a square face shape. 
  • Round: Round faces have soft curves and are the same width from the jaw to the forehead.
  • Heart: A heart-shaped face is the widest at the forehead, with a narrow chin and high cheekbones.
  • Triangle: If you have a wider, square-shaped jaw but a narrower forehead, you probably have a triangle face shape.
  • Diamond: A diamond face has a narrower forehead and jaw with defined cheekbones.

What Other Measurements Do You Need for Glasses? 

Besides your glasses or face size, you’ll also need your eyeglass prescription measurements when buying new glasses. Other vital measurements from your prescription include:

  • Pupillary distance (PD): Your PD is the measurement between the pupils of your eyes.
  • Segment height (SH): You’ll need your SH if you have progressive lenses or bifocals. SH is the distance from your lenses’ bottom to the top line of a bifocal or the beginning of the progressive addition.
  • Ocular center (OC): The OC is the vertical measurement from the bottom of the lens to the center of the pupil, which should also be the center of the lens.

Shop for Glasses From Lensabl

Getting glasses with the right fit is crucial for both style and comfort. Whether you use the measurements on your current pair of frames or you decide to measure your face for the right fit, getting accurate measurements helps you pick glasses that are right for you.

In the market for some new frames? At Lensabl, we aim to make vision easy and affordable for all. We offer a more convenient option for buying new frames or contacts or replacing the lenses in frames you already love.

Shopping through Lensabl saves you an average of 70% compared with optician prices, keeping more money in your pocket while providing you with the high-quality vision products you need. As a one-stop shop for all your vision care needs, we also provide a vision benefits plan for those who regularly need vision products.

To find the perfect glasses for you, browse our frames today. You can also check out our FAQ page for more answers to your questions.