Glasses measurement: how to know your frame size?

Lensmart 2022-11-28 15:53:25

While you can immediately purchase eyeglasses at the store, some are meticulous enough who will inspect the measurements before buying. In reality, there are specific frame sizes for your favorite eyeglasses.


Continue reading to know more about these measurements and how you can determine your frame size.


high-quality glasses from Lensmart

What are glasses measurements?

Suppose you feel like the eyeglasses fit like gloves; finding the suitable frame sizes for your next pair of glasses is straightforward. For those who want to do it manually, you can measure the frame from end to end with a ruler. You can use these measurements as a guide when you shop for new glasses. Besides a ruler, you can also use a measuring tape.


Also, keep in mind that sunglasses are relatively larger in terms of measurements than eyeglasses. Hence, the sunglasses will have a different size than your pair of prescription glasses. As you already know, the measurements of your glasses are stamped on the temple or the nose bridge.


Here is how to identify the specific measurements of your frames.

1.Bridge width:; The shortest distance between the edges of two lenses which involves two digit-numbers ranging from 14-24.

2.Frame width(Lens width): The distance between two vertical lines cut outside the left and right lenses with two-digit number between 40-62.

3.Frame height(Lens height): The distance between two horizontal lines cut the top and bottom of two lenses.

4.Temple length: The length of the temple from the center of each hinge to its temple tip. It's a three-digit number ranging from 120 to 150.

the measurements of eyeglasses 

Your eye size is a significant number you must closely look into. Depending on the frame style you prefer, you can either go up or down by one and still find a decent frame fit. Glasses measurement fitting within 2-3 millimeters is still a perfect fit. Hence, you may wear them comfortably even if you do not get the exact frame size.


Why is glasses measurement so important?

Of course, you do not want to wear oversized glasses unless it's part of your fashion style. But with reading or prescription glasses or any sunglasses you need to wear daily, glasses measurement must be accurate. 

While not all can manually measure their frame sizes accurately and send the measurement to the manufacturers, eyeglasses makers today have varying measurements for every size. All you need to do is manually have your glasses measured and compare these measurements to the ones provided by the glasses store of your choice.


Technically, eyeglasses that are too narrow make one's face look wider. Meanwhile, a too wide frame makes the faces narrower—besides the nice appearance of the glasses measurement, getting the correct sizes will bring comfort to wearers. If you're always wearing these glasses, you need to be comfortable with them, and having the exact measurements will do just that.


How to measure glasses frame size?

Here are some tips for making glasses measurements before purchasing your frames. Usually, the parameters of the size of the glasses are marked on the temple arms, the bridge or the label. The frame dimensions are showed in two forms based on different methods of measuring: square method and datum line method.

1. Square method

Square method refers to the square formed by horizontal and vertical tangents, which are respectively made at the horizontal and vertical outer edges of the inner edge of the frame (i.e. the outside of the lens). The longest length of the left and right lenses in the horizontal direction is the frame width, and the shortest distance between the edges of two lenses is the bridge width.


The frame dimensions are usually indicated on the inside of the temple arms. A "□" mark indicates the square method. For example, “56□14-140” uses the square method, representing that the frame width is 56 mm, the bridge width is 14 mm, and the temple length is 140 mm. Most glasses frames in China are showed in such form.


example of the square method

2. Datum line method

Datum line method refers to making horizontal tangents at the highest and lowest points of the outside of the two lenses, then taking the bisector in the vertical direction as the center point, and making parallel lines of the horizontal tangents (i.e. the line through the geometric center points of the two lenses) as the datum line. The above method is also the method to measure the datum line.


Imported frames or some high-end frames are expressed by datum line method. It is also marked on the inside of the temple arms. A "-" mark indicates the use of datum line method, such as 56-16-135, representing the frame width is 56 mm, the bridge width is 16 mm, and the temple length is 135 mm.

example of the datum line method

How to select glasses frames according to the size?

There are two situations of unsuitable frame size: one is the size is too large, the other is too small.


A pair of inappropriate glasses not only fails to achieve an ideal outcome of the correction, but also may be harmful to wearers' eyes. Frames that are too large are easy to fall off and break up, and then you may be scratched by broken lenses.


However, the line between large and small frame sizes is vague. There is no clear standard to define that how many millimeters of the frame belongs to large size, or in what specific range the frame size is small.


Whether the glasses frame is big or small, mainly have something to do with specific wearers. So how to avoid improper frames? How do you get the best frame for yourself? Our suggestions are at the following :

1. The width of your face should be consistent with the frame width.

2. The width of the head should be consistent with the distance between two temple arms.

3. The distance between the ear and the eye should be consistent with the temple length. Otherwise, too long or too short will make you feel discomfortable.

4. If the wearer has a low nose bridge, it is better to choose frames with nose pads (especially when the left and right nose pads are close). This is because nose pads can hold the frame in place, preventing it from falling off, and also support the lenses to make it have a distance to your eyes. 

From these four aspects to choose the frame and then the size, there will be no problem to select a pair of suitable glasses, so that you can comfortably wear glasses and get a better vision.


Additional advices

1. If the index is high, you can choose a frame with smaller lens size, so that your lens seems thinner.

2. If you choose progressive lens, your glasses frame should not be too large, since the lens will be cut less in large frames, which will keep more blurry area. The near area of progressive lens is close to the nose, so we should not pick frames that need cut off the part of lens near the nose. In order to ensure that there is enough area to see near and far, the frame height should be at least 33mm to meet the requirements of cutting and assembly.

Face shape guide for choosing glasses

1. What glasses suit oval face?

It is a fact that those people who have oval face have evenly proportioned face features that mean they can easily wear all shapes of glasses. It is a versatile shape and all frames go well with the oval face. Square eyeglasses, cat eye glasses, and geometric eyeglasses all suit for your oval face shape. You can select the frame of your choice accordingly.

glasses for oval face

2. What glasses suit round face?

In the round face, the equal dimension is noted and the face is wide. The soft jawline is noted in those people who have a round face shape. The eyeglasses that look best on the round face includes: Wayfarers, rectangular, aviators, oversized, square, geometric, and navigators. The sharp angle of the mentioned eyeglasses works best in order to complement the round face soft lines.

glasses for round face

3. What glasses suit diamond face?

In the diamond face, the cheekbones and forehead look wider with a narrow chin and jawline. It is a desirable face shape and most people love to have this type of face shape because it gives an attractive look. 

The best eyeglasses for this type of face shape are: Square aviator eyeglasses, aviator eyeglasses, round square eyeglasses, square eyeglasses, round rectangle eyeglasses, and rectangle eyeglasses. Choose the frame and give your face an alluring look at the friend's party.

glasses for diamond face

4. What glasses suit heart face?

In the heart face, the chin seems typically pointed with the widest forehead on the face. Oval eyeglasses look ideal on the heart face shape because they balance as well as soften the face angles. These eyeglasses never overemphasize the cheekbone and thus, giving your face a classy look.

glasses for heart face

5. What glasses suit pear face?

Pear face tends to have cheekbone which is less prominent with a broad jawline and narrow forehead. This is also known as a triangle face because of the strong jawline. The eyeglasses that look best on the pear-shaped face include: Angular square eyeglasses, smaller round shape eyeglasses, and aviators. 

When you have a pear face and wear angular square eyeglasses, people admire the beauty on the face and you can confidently enjoy the kitty parties because these eyeglasses give an attractive appearance.

glasses for pear face

6. What glasses suit oblong face?

The main characteristic of the oblong face is the balanced features of the face. The length is twice as long as wide with the jaw being narrow. The chin looks narrower than the forehead and the cheekbones are high in oblong face. 

The most interesting fact is that in the oblong-shaped face, the faces look a bit longer but less wide. It is easy to choose eyeglasses for oblong faces because you can choose any style of eyeglasses frame. 

Cat eye glasses, browline eyeglasses, geometrically square eyeglasses, and rectangular eyeglasses are best suitable for oblong faces and enhance the features of the face. Rock these shapes of eyeglasses on the oblong face without any fear of doing wrong.

glasses for oblong face


Finally, not everyone knows that there are specific measurements on your eyeglasses and sunglasses. Now that you have these glasses measurement guides, you check your frame sizes. Knowing your frame glasses measurement allows you to have your glasses customized. Also, it can be your guide when shopping for glasses online.

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