Screen size is measured diagonally from corner to corner, in inches

Computer screen size refers to the distance from one corner of the display to the opposite corner, measured diagonally across the glass or panel. This diagonal measurement is always given in inches. A 24-inch monitor, for example, measures 24 inches from the bottom-left corner to the top-right corner. This is the standard used by every manufacturer — Dell, LG, ASUS, HP, and others — so the number on the box tells you exactly what you are getting.

The diagonal measurement matters because it accounts for both width and height at once. Two monitors might have different shapes — one wider, one taller — but if they share the same diagonal measurement, they occupy roughly the same physical space on your desk. This is why manufacturers use it instead of width or height alone.

The screen size does not include the bezel, the plastic or metal frame around the glass. It measures only the visible display area where the image actually appears.

Key Takeaways

  • Screen size is always the diagonal measurement in inches, from one corner to the opposite corner, and does not include the frame around the display.
  • You can measure a screen yourself with a tape measure or ruler, starting from the bottom-left corner and stretching to the top-right corner.
  • The spec sheet or manual for your monitor will list the screen size, and you can also find it by searching the model number online.
  • Common desktop monitor sizes are 21.5, 24, 27, 32, and 34 inches; laptop screens typically range from 13 to 17 inches.
  • Screen size alone does not determine image quality — resolution, refresh rate, and panel type matter equally for what you actually see.

How to measure your screen yourself with a tape measure

If you want to verify the size of a monitor you already own, use a cloth tape measure or a flexible ruler. Start at the bottom-left corner of the screen glass itself, not the frame. Stretch the tape diagonally across to the top-right corner. Write down the number where the tape ends. That measurement, rounded to the nearest half-inch or whole inch, is your screen size.

Use the glass edge, not the plastic bezel. The bezel can vary in thickness between models, so measuring from the frame will give you a number that does not match the manufacturer's spec. If your tape measure is not long enough, you can use a piece of string, mark where it reaches the opposite corner, and then measure the string against a ruler.

Most screens measure out to within a quarter-inch of the advertised size. If you measure 23.75 inches on a monitor labeled 24 inches, that is normal and expected.

Finding the screen size from your monitor's model number or manual

The easiest way to find your screen size is to look at the monitor itself or its documentation. The model number is usually printed on the back of the monitor or on a sticker on the base. Search that model number on the manufacturer's website — Dell, LG, ASUS, BenQ, and others all publish spec sheets that list the screen size in the first few lines.

If you have the original box or manual, the screen size appears on the front of the box and in the specifications section of the manual. If you bought the monitor used and no longer have the box, the manufacturer's website is your fastest route. Type the model number into Google along with the word "specs," and the official product page usually appears in the top results.

For a laptop, the screen size is often printed on the bottom of the lid or in the system settings. On Windows, right-click the desktop, select Display Settings, and scroll down to find the screen resolution and sometimes the diagonal size. On Mac, go to System Preferences, then Displays, where the size may be listed. If it is not, search your laptop model number plus "screen size" online.

Common screen sizes for desktops and laptops

Desktop monitors come in a standard range of sizes. The most common are 21.5 inches, 24 inches, 27 inches, 32 inches, and 34 inches. A 24-inch monitor is the current standard for office work and general use. A 27-inch monitor gives you more screen space without taking up dramatically more desk room. Larger monitors — 32 and 34 inches — are popular for video editing, graphic design, and gaming, where the extra space justifies the cost and desk footprint.

Laptop screens are smaller because they sit on your lap or a small desk. Common sizes are 13 inches, 14 inches, 15.6 inches, and 17 inches. A 13-inch laptop is highly portable but cramped for long work sessions. A 15.6-inch laptop balances portability with usable screen space. A 17-inch laptop is bulky to carry but gives you nearly as much screen real estate as a small desktop monitor.

Ultrawide monitors — 34 inches and larger — have a wider aspect ratio than standard monitors. They still measure diagonally the same way, but the width is stretched, giving you more horizontal space for spreadsheets, video timelines, or side-by-side windows.

Why screen size alone does not tell you about image quality

A larger screen does not automatically mean a sharper or better image. What you actually see depends on three things working together: screen size, resolution, and pixel density. Resolution is the number of pixels — tiny dots of light — that make up the image, measured in width by height. A 24-inch monitor with 1920 by 1080 resolution has the same number of pixels as a 27-inch monitor with the same resolution, but they are spread across a larger area on the 27-inch screen, so each pixel is slightly larger and the image may look less sharp.

Refresh rate — how many times per second the screen redraws the image — also matters for smoothness, especially in gaming or video work. A monitor's panel type (IPS, VA, or TN) affects color accuracy and viewing angles. A large, cheap monitor with low resolution and a poor panel type will look worse than a smaller, well-made monitor with high resolution and good color reproduction.

When you are choosing a monitor, look at the screen size, resolution, refresh rate, and panel type together. A 27-inch monitor with 2560 by 1440 resolution will look sharper than a 27-inch monitor with 1920 by 1080 resolution, even though they are the same size.

Aspect ratio: why some screens are wider or taller

Aspect ratio is the relationship between a screen's width and height. The most common aspect ratio for desktop monitors is 16 by 9, which means the screen is 16 units wide for every 9 units tall. This is the standard for most work and gaming monitors. A 24-inch monitor with a 16 by 9 aspect ratio will be roughly 21 inches wide and 12 inches tall.

Some monitors use a 16 by 10 aspect ratio, which is slightly taller relative to the width. Ultrawide monitors use a 21 by 9 aspect ratio, making them much wider and narrower than standard monitors. A 34-inch ultrawide monitor is wider than a standard 27-inch monitor but shorter in height.

The aspect ratio does not change how you measure screen size — you still measure diagonally from corner to corner. But it does change the physical shape of the monitor and how much horizontal or vertical space you get. If you spend a lot of time with spreadsheets or code, a taller aspect ratio (like 16 by 10) gives you more vertical space. If you edit video or work with timelines, an ultrawide aspect ratio gives you more horizontal space.

Frequently Asked Questions

Does screen size include the frame around the monitor?

No. Screen size measures only the glass or panel where the image appears. The plastic or metal frame around it, called the bezel, is not included in the measurement. If you measure your monitor yourself, start from the edge of the glass, not the edge of the frame.

What is the difference between screen size and resolution?

Screen size is the physical diagonal measurement of the display in inches. Resolution is the number of pixels that make up the image, expressed as width by height — for example, 1920 by 1080. A 24-inch monitor and a 27-inch monitor can have the same resolution, but the pixels are larger on the 27-inch screen because they are spread across more space.

Can I use a phone screen size chart to measure my monitor?

No. Phone screens are measured the same way — diagonally in inches — but a phone screen size chart is designed for phones, not monitors. The sizes and aspect ratios are different. Measure your monitor directly with a tape measure, or search the model number for the official spec sheet.

Is a 27-inch monitor too big for a small desk?

It depends on how far you sit from the screen and how much desk space you have. Most people sit 24 to 30 inches from their monitor. At that distance, a 27-inch monitor is comfortable for most work. If your desk is very small or you sit very close to the screen, a 24-inch monitor may be easier on your eyes. If you have the space and sit at a normal distance, a 27-inch monitor is not too large.

Why do some monitors list two different sizes?

Some manufacturers list both the viewable screen size and the total panel size. The viewable size is what you actually see — the diagonal measurement of the glass. The total panel size includes a small border of the panel that is hidden behind the bezel. Always use the viewable size when comparing monitors, as that is the standard the industry uses.