How To Measure a Computer Screen

You can use a measuring tape or other methods

What To Know

  • Screen size is the diagonal length from the top corner to the opposite bottom corner. 
  • It is measured in inches and is different from screen resolution, which is in pixels.
  • Do not include the bezel around the screen when measuring the size.

This article explains how to measure a computer screen using a tape measure or a simple mathematical equation.

How To Measure Monitor Size With a Measuring Tape

Desktop computers and laptops come in different screen sizes. It is as essential as screen resolution as it is critical to productivity. The correct measurement can also help you figure out the size of a screen filter you need to buy.

Screen size is the actual physical size of the screen and is in inches. The simplest method to measure a computer monitor is with a measuring tape or a ruler. 

The computer or the laptop manual will mention the monitor size. Manufacturers sometimes display it on a sticker on the device. But if you can’t spot it anywhere, you can measure the size of your existing monitor or a new one you are interested in buying with the help of a measuring tape. 

  1. Use a measuring tape of sufficient length.

  2. Start at the top-left corner and extend it along the diagonal to the opposite bottom-right. If you start from the top-right corner, pull it straight to the bottom-left corner.

    Measuring screen size

    Saikat Basu

  3. Measure only the screen and not the bezel or the casing around the screen.

  4. The diagonal measure is the screen size.


An online search is the fastest way to find the precise size of the computer monitor. Type the make of your computer monitor or laptop and any model number that tail them in a search engine, and you will get the detailed specifications with the screen size. You can also get these details from the manufacturer’s website.

How To Measure Monitor Size With Simple Math

The Pythagorean theorem is an alternative method to measure a computer monitor. It states in a right-angled triangle, the square of the hypotenuse side is equal to the sum of squares of the other two sides. In a computer monitor, the hypotenuse is the diagonal measure that gives you the screen size. 

Measure the width and height of the screen, square the screen’s width and the height, and add the two numbers together. Calculate the square root of this sum to get the diagonal measurement and the screen size. 

For instance, a Dell XPS 13 has a screen width of 11.57 inches and a height of 6.51 inches

Multiply the width by itself to get 133.8. Then multiply the height by itself to get 42.38. Add the two numbers together (133.8+42.38 =176.18). Find the square root of the sum (√176.18 = 13.27). 

13.3 inches is the advertised size of a Dell XPS 13 laptop monitor.


There are online calculators like Omni Calculator that quickly estimate the dimensions with the diagonal, width, or height. Enter one, and it will automatically calculate the other two measurements.

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