Knowing how to measure a monitor is helpful when buying a new one, choosing a proper desk setup, or checking compatibility with a wall mount. Monitors are measured differently than you might expect, so it’s important to use the right method to get accurate results. Here is how to measure a monitor step by step.
- Measure the Screen Diagonally
The size of a monitor is measured diagonally from one corner of the screen to the opposite corner. This means from the top-left corner of the visible screen area to the bottom-right corner—or vice versa.
Do not include the plastic frame or bezel around the screen in this measurement. You want to measure only the actual display area that lights up.
Use a tape measure or ruler. Stretch it from one visible corner to the other and take note of the measurement in inches, as monitor sizes are usually expressed in inches (e.g., 21.5″, 24″, or 27″).
- Measure Height and Width (Optional but Useful)
In some cases, knowing the screen’s height and width is also helpful, especially if you’re planning to fit it into a cabinet or mount.
To get the width, measure across the screen from left to right, again ignoring the bezel.
To get the height, measure from the bottom edge of the display area to the top.
If you’re including the bezel (frame), make sure to note that separately so it doesn’t confuse the actual screen size.
- Check the Aspect Ratio
Many monitors follow a common aspect ratio, such as 16:9 (widescreen), 16:10, or 21:9 (ultrawide). If you know the width and height, you can figure out the aspect ratio by dividing the width by the height and comparing the result.
For example, if a screen measures about 20 inches wide and 11.25 inches tall, the ratio is 20 ÷ 11.25 = 1.78, which is close to 16:9.
- Confirm with Manufacturer Specifications
If you’re unsure whether your measurements are accurate, you can usually find the model number of your monitor on a sticker at the back. Use this number to search online and find the manufacturer’s official screen size and specs.
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