Monitor size is measured diagonally across the screen, corner to corner, in inches

Your monitor's size is the distance from the bottom-left corner to the top-right corner of the screen itself — not including the plastic frame around it. This diagonal measurement is always given in inches. A 24-inch monitor means 24 inches measured that way. Most monitors sold today range from 21 inches on the small end to 32 inches or larger, though 24 and 27 inches are the most common sizes you'll find.

The reason manufacturers measure diagonally instead of by width or height is historical — it's the standard that stuck. But it matters for you because it's the only number you'll see on the box, on the manufacturer's website, and on price tags. When you're shopping or trying to figure out what you already own, diagonal is what you're looking for.

Key Takeaways

  • Monitor size is always the diagonal measurement in inches, from one corner of the screen to the opposite corner, not including the frame.
  • You can measure your own monitor with a tape measure or ruler, starting at the bottom-left corner of the actual screen and going to the top-right corner.
  • The model number or specifications on the back of your monitor, in your purchase receipt, or on the manufacturer's website will tell you the exact size.
  • Screen resolution (how many pixels fit on the display) is separate from size — a 24-inch monitor and a 27-inch monitor can have the same resolution.
  • The physical width and height of your monitor vary depending on its aspect ratio, so diagonal is the only consistent measurement across different models.

How to measure your monitor yourself

If you want to know your monitor's size right now, grab a tape measure or a ruler and measure from the bottom-left corner of the screen to the top-right corner. Make sure you're measuring the actual screen — the glass or plastic display surface — not the black plastic bezel (frame) around it. Start at the very corner where the screen begins, not where the frame starts.

Measure in a straight diagonal line. If you're using a ruler that's not long enough, you can measure the width and height separately, then use a calculator. Measure the width of the screen from left to right, and the height from top to bottom. Then use the Pythagorean theorem: multiply the width by itself, multiply the height by itself, add those two numbers together, and take the square root. That gives you the diagonal. For example, a screen that's 20 inches wide and 11 inches tall would be about 22.7 inches diagonally.

Your measurement might not be a round number. That's normal. Manufacturers round to the nearest inch for the official size, so a monitor that measures 23.8 inches diagonally is sold as a 24-inch monitor.

Finding the size from your monitor's information

The easiest way to find your monitor's size is to look it up rather than measure it. Check the back or bottom of your monitor for a model number — it's usually printed on a sticker or label. Write down that model number and search for it on the manufacturer's website (Dell, LG, ASUS, HP, and others all have searchable product databases). The specifications page will list the screen size right at the top.

If you bought the monitor recently, check your receipt or your email confirmation. The size is always listed in the product name or description. You can also check your computer's display settings. On Windows, right-click on the desktop, select "Display settings," scroll down, and look for "Display information" — it won't always show the size, but sometimes it does. On Mac, go to the Apple menu, select "System Settings," click "Displays," and the resolution and size information appears there.

If you have the original box, the size is printed on it, usually on the front and back. Even if you threw the box away years ago, the model number on your monitor will get you to the answer in under a minute.

Why monitor size matters for your setup

Monitor size affects how much space you have to work with on your screen. A 24-inch monitor is comfortable for most office work, web browsing, and everyday tasks. A 27-inch monitor gives you more room to see multiple windows at once or to work with detailed images. Larger monitors — 32 inches and up — are useful if you're doing video editing, photo work, or if you sit far back from your desk.

Size also affects how close you need to sit. A general rule is to sit about one arm's length away from your monitor, with the top of the screen at or slightly below eye level. If your monitor is very large, you may need to sit farther back, or you'll find yourself turning your head to see the whole screen. If it's very small, you might strain your eyes trying to read text.

The physical footprint of your monitor — how much desk space it takes up — depends on both the size and the aspect ratio (whether it's a standard rectangle or an ultrawide). A 27-inch standard monitor is wider than a 24-inch one, so measure the width and depth of your desk space before buying a larger screen.

Monitor size versus resolution

Monitor size and resolution are two separate things, and it's easy to mix them up. Size is the diagonal measurement in inches. Resolution is how many pixels (tiny dots of color) fit on the screen — usually written as something like 1920 × 1080 or 2560 × 1440.

You can have two monitors that are the same size but different resolutions. A 24-inch monitor might have 1920 × 1080 pixels, while another 24-inch monitor has 2560 × 1440 pixels. The second one will show sharper text and images because more pixels are packed into the same physical space. You can also have two monitors with the same resolution but different sizes — a 27-inch and a 32-inch monitor might both have 2560 × 1440 resolution, but text and images will appear larger on the 32-inch screen because the same number of pixels is spread across a bigger area.

When you're shopping for a monitor, both size and resolution matter for what you're trying to do. If you work with spreadsheets or code, a higher resolution on a smaller screen keeps text sharp and readable. If you watch videos or do creative work, a larger screen with good resolution gives you more to work with.

Common monitor sizes and what they're used for

Most monitors fall into a few standard sizes. A 21 or 22-inch monitor is small and takes up minimal desk space — useful if you're tight on room or using it as a secondary display. A 24-inch monitor is the most popular size for general office work, gaming, and everyday use. It's large enough to be comfortable but small enough to fit on most desks without taking over.

A 27-inch monitor is the next step up and is common for people who do detailed work like photo editing, video work, or programming. It gives you noticeably more screen space without being so large that you have to move your head constantly. A 32-inch monitor or larger is usually chosen by people doing professional creative work, or by people who like having a lot of screen space for multitasking. These are less common in home offices because they take up significant desk space and can feel overwhelming if you sit close to them.

Ultrawide monitors — which are wider than they are tall — come in sizes like 29, 34, and 49 inches. These are measured diagonally like any other monitor, but they give you a lot of horizontal space, which some people prefer for video editing, trading, or gaming. They're not standard, so they're less common and usually more expensive than a regular monitor of the same diagonal size.

Frequently Asked Questions

Does the frame around the screen count toward the monitor size?

No. The size measurement is only the screen itself — the glass or plastic display surface. The plastic bezel (frame) around it is not included. When you measure or look up your monitor's size, you're measuring only the visible display area.

Why do monitor sizes seem odd, like 23.8 inches instead of 24?

Manufacturers build monitors to specific width and height dimensions, and the diagonal measurement comes out to something like 23.8 or 27.5 inches. They round to the nearest whole number for marketing — so 23.8 becomes "24-inch" on the box. The actual screen is slightly smaller than the advertised size, but the difference is small enough that it doesn't matter in practice.

Can I use my monitor size to figure out if it will fit on my desk?

Not directly. A 27-inch monitor could be 24 inches wide and 14 inches tall, or it could be wider or taller depending on its aspect ratio. Measure the actual width and depth of the monitor itself, or check the specifications on the manufacturer's website for the exact dimensions. Then compare those to your available desk space.

Is a bigger monitor always better?

Not necessarily. A bigger monitor gives you more screen space, but it also takes up more desk room and can cause eye strain if you sit too close. The right size depends on how far you sit from your monitor, what you use it for, and how much desk space you have. Most people find 24 to 27 inches comfortable for everyday work.

What if my monitor doesn't have a model number I can find?

If the model number isn't on the back or bottom, check the original box, your receipt, or your computer's device manager. On Windows, right-click the desktop, select "Display settings," scroll down to "Advanced display settings," and look for the monitor name. That name usually includes the model number. If you still can't find it, measuring the screen yourself with a tape measure is quick and accurate.