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How To Measure a Monitor

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Desktop monitors and laptop screens vary in size. It can range from 13 inches to 43 inches. Some users even utilize a TV as a monitor letting them expand their monitor size up to 84 inches or more. But how do you measure the size of their monitor in inches? 

Quick Answer

The easiest way to determine your screen size is by using a measuring tape to measure it diagonally. But if you don’t have a measuring tape but know the height and width of the monitor, you can use simple math (Pythagorean Theorem) to determine the size of the screen. 

Knowing how to measure the size of a monitor is helpful, particularly when you want to upgrade your computer monitor. Knowing how it’s being measured will give you an idea of the expected size of any monitor you may be interested in buying.

Keep reading to learn more about how to measure a monitor. 

How To Measure the Size of Your Monitor

While an online search is the fastest way to tell the size of any monitor, provided you know the monitor’s model number. By doing an internet search on the model number of a monitor, you get the monitor’s size and a detailed specification of the monitor, such as aspect ratio, resolution in pixel, and so on. 

However, if you do not want to do an internet search on the monitor and want to confirm the monitor’s measurement, you can measure it yourself. There are a few ways to measure your monitor size, but in this article, we will discuss two ways you can go about it. 

Method #1: Using a Measuring Tape

When you want to measure your monitor screen with a measuring tape, you must take the measurement diagonally. That is, you are to measure from the top end of the monitor to the bottom end of the screen at the other end. You are to measure the size of the screen in inches. 

Here’s how to measure the size of your monitor using a measuring tape.

  1. Get a measuring tape with sufficient length. 
  2. Place one end of the measuring tape on the top-right corner of the screen. 
  3. Extend the measuring tape diagonally to the opposite end at the bottom left of your screen 
  4. Whatever number you have on your measuring tape is the approximate size of your monitor screen. 

Method #2: Using the Pythagorean Theorem 

You can also find your screen’s size by measuring the screen’s height and width. But when you measure the height and width, you will also have to do simple math (Pythagorean Theorem). Since your TV is a rectangle, you get two equal triangles when you measure the two sizes and draw a diagonal line in the rectangle. The hypotenuse of the two triangles is the size of your screen. 

Here’s how to measure the size of your monitor using the Pythagorean Theorem.

  1. Use your measuring tape to measure the width and height of your monitor screen in inches. 
  2. Add the square of the width with the square of the height. 
  3. Find the square root of the value you got; whatever your answer is, that is your screen size in inches.  
Keep in Mind

When measuring the size of your monitor, do not include the bezel around the screen.


Keep in mind that you can always check the information of any monitor online by searching for its model number. But you can always measure the screen size yourself using a measuring tape. And remember to measure from one top corner of the screen to the other bottom corner of the screen; that is diagonal. Although you can measure the height and width, use the Pythagorean formula to calculate the diagonal. 

Frequently Asked Questions 

Why are monitor screens measured diagonally? 

The reason the monitor’s screen is measured diagonally and not horizontally is partly to have a traditional way to measure screens and partly for marketing reasons. Since it is generally accepted that monitors are measured diagonally, there will not be miscommunication in labeling monitor screen size.

Also, when you measure a screen diagonally, it is the largest distance between any two points on the screen. So, it gives an impression of a larger viewing surface. 

Why does the aspect ratio of a screen matter? 

The aspect ratio of a screen is the proportional relationship between the height and width of the screen. It is expressed as two numbers separated by a color, such as x:y, where x is the width and y is the height. The aspect ratio of the screen matters because it tells you the size of the image you can fit perfectly on the TV. 

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