Measure diagonally from corner to corner

Screen size is always the diagonal measurement from one corner of the display to the opposite corner, measured in inches. This is the only standard that matters—not the width, not the height, just the diagonal. A 24-inch monitor means the distance from the bottom-left corner to the top-right corner is 24 inches.

To measure your own screen, you need a measuring tape or ruler. Extend it from the bottom-left corner of the screen itself (not the bezel or frame around it) to the top-right corner. Keep the tape straight and taut. Write down the number in inches. If you get 21.5 inches, your screen is a 22-inch display. If you get 27.2 inches, it's a 27-inch screen.

The reason manufacturers use diagonal measurement is historical—it's the easiest single number to compare across different aspect ratios. A 24-inch ultrawide monitor and a 24-inch standard monitor have the same diagonal but very different widths and heights.

Key Takeaways

  • Screen size is always measured diagonally from corner to corner in inches, not width or height.
  • Measure from the actual display surface, not the plastic or metal frame around it.
  • If you cannot physically measure, check your monitor's manual, the manufacturer's website, or your computer's display settings.
  • The diagonal measurement is the only number that matters when comparing screen sizes across different monitor types.
  • Common desktop screen sizes are 21.5, 24, 27, 32, and 34 inches; laptop screens typically range from 13 to 17 inches.

Find your screen size in your computer's settings

If you cannot or do not want to measure physically, your operating system can tell you the screen size. On Windows, right-click the desktop and select Display settings. Scroll down to the Display section. The size is not always listed here, but the resolution (like 1920 × 1080) is. Write down that resolution.

On macOS, click the Apple menu, select System Settings, then Displays. The resolution appears, but the physical screen size usually does not. Again, note the resolution.

Once you have the resolution, you can cross-reference it with your monitor's manual or the manufacturer's website. Search for your monitor brand and model number (usually printed on the back or bottom of the screen). The manual or product page will list the screen size in inches. This is faster than measuring if you know your monitor's exact model.

Check your monitor's manual or label

Most monitors have a label on the back or bottom that lists the model number and sometimes the screen size directly. Look for a sticker or printed text. The model number is your fastest path to the answer—search that number plus the brand name on the manufacturer's website, and the product page will confirm the screen size.

If you have the original manual or packaging, the screen size is printed on the box and inside the documentation. For laptops, the screen size is usually printed on the bottom of the lid or in the system information menu. On Windows, press Windows key + Pause/Break or search System Information to see your device name and specs, though the screen size may not appear here.

For older monitors or secondhand equipment, the label may be worn or missing. In that case, the diagonal measurement with a tape measure is your most reliable option.

Understand how screen size relates to resolution

Screen size and resolution are separate things, and many people confuse them. A 24-inch monitor can have a resolution of 1920 × 1080 or 2560 × 1440—both are 24 inches diagonally, but one is sharper because it packs more pixels into the same space. The resolution tells you how many pixels fit on the screen; the size tells you how big the screen physically is.

This matters because a 27-inch monitor at 1920 × 1080 will look blurry compared to a 27-inch monitor at 2560 × 1440. The pixels are larger on the first one. Conversely, a 24-inch monitor at 2560 × 1440 will have very small, sharp text and icons. Neither is wrong—it depends on how far you sit from the screen and what you use it for.

When you measure or look up your screen size, you now know it is independent of how sharp the image is. A 32-inch screen could be 4K (very sharp) or 1440p (less sharp). The diagonal measurement alone does not tell you.

Measure the bezel separately if you need the actual display area

The bezel is the plastic or metal frame around the screen. When you measure diagonally, you measure only the lit display area, not the bezel. If you need to know how much desk space the monitor will take up, you should measure the entire width and height of the monitor including the bezel and stand.

For most purposes—comparing screen sizes, replacing a monitor, or understanding what you have—the diagonal measurement of the display itself is all you need. But if you are fitting a monitor into a tight space or mounting it on a wall, measure the full width and height of the entire unit, including the stand or mounting bracket.

Some monitors have very thin bezels and some have thick ones. A 27-inch monitor with a thin bezel takes up less desk space than a 27-inch monitor with a thick bezel, even though they are the same screen size. The diagonal measurement does not capture this difference.

Common screen sizes for desktops and laptops

Desktop monitors come in standard sizes: 21.5, 24, 27, 32, and 34 inches are the most common. A 24-inch monitor is a good general-purpose size for most desk setups. A 27-inch monitor is popular for gaming and detailed work. A 32-inch monitor is large and requires more desk space. Ultrawide monitors at 34 inches or larger are specialized for video editing, programming, or trading.

Laptop screens are smaller. Most laptops have screens between 13 and 17 inches. A 13-inch laptop is portable and light. A 15-inch or 16-inch laptop is more common for everyday use. A 17-inch laptop is larger and heavier but gives you more screen space. These sizes are measured the same way—diagonally—but the aspect ratio is usually wider on a laptop than on a desktop monitor.

Tablets and phones also use diagonal measurement. A typical smartphone screen is 6 to 7 inches. A tablet is usually 10 to 12 inches. The principle is the same: corner to corner, diagonally, in inches.

Why manufacturers do not always print the size on the monitor itself

Many modern monitors, especially budget models, do not have the screen size printed anywhere visible. Manufacturers assume you already know the size when you buy it, or they expect you to look it up online. This is frustrating if you inherit a monitor or buy a used one without documentation.

The model number is your best clue. It is usually on the back or bottom. Search the brand and model number on the manufacturer's website, and you will find the screen size listed in the product specifications. If you cannot find the model number or the website is no longer active (common with older equipment), measuring diagonally with a tape measure is your fallback.

Some monitors have the size printed very small on the back panel, so check carefully before you assume it is missing entirely.

Frequently Asked Questions

Do I measure the screen or the whole monitor including the frame?

Measure only the lit display area, not the plastic or metal frame around it. Place your measuring tape at the corner of the actual screen where the image appears, not at the edge of the bezel. This is how manufacturers measure, and it is the standard everyone uses.

What if my measurement does not match a standard size?

You probably measured from the bezel instead of the display, or your tape was not perfectly straight. Try again, starting at the very corner of the lit area. If you get 23.8 inches, that is a 24-inch monitor—manufacturers round to the nearest inch. If you get 26.9 inches, that is a 27-inch monitor.

Can I find my screen size in Windows or Mac settings?

The operating system shows resolution (like 1920 × 1080) but usually not the physical screen size in inches. You can use the resolution to search the manufacturer's website, or you can look up your monitor model number. Both methods are faster than measuring if you have that information available.

Is screen size the same as screen resolution?

No. Screen size is the diagonal measurement in inches. Resolution is the number of pixels, like 1920 × 1080. A 24-inch monitor and a 27-inch monitor can have the same resolution, but the pixels will be larger on the 24-inch screen. They are independent measurements.

What is the difference between a 24-inch and a 27-inch monitor in real use?

A 27-inch monitor gives you more screen space and is easier to read from a distance, but it takes up more desk space and may require you to move your head more to see the corners. A 24-inch monitor is compact and good for small desks. The choice depends on your desk size and how far you sit from the screen.