Measure Your Monitor Diagonally From Corner to Corner
Monitor size is always measured diagonally across the screen, from one corner to the opposite corner. This is the only measurement that matters when you see a monitor listed as 24 inches, 27 inches, or 32 inches. You measure from the inside edge of the bezel (the plastic frame around the screen) to the inside edge on the opposite side—not the outer edges of the plastic casing.
Use a soft measuring tape, the kind tailored shops use, because it bends around curves without kinking. If you only have a rigid ruler or metal tape measure, you can lay a string diagonally across the screen, mark where it touches each corner, and then measure the string against a ruler. Measure in inches if you want to match the standard monitor labels you see in stores.
The diagonal measurement is what determines how much screen real estate you actually have. Two monitors with the same diagonal size but different aspect ratios (like 16:9 versus 21:9) will have different widths and heights, but the diagonal stays the same.
Key Takeaways
- Monitor size is always the diagonal measurement from the inside of one corner to the inside of the opposite corner, measured in inches.
- Measure only the screen itself, not the plastic bezel or the stand—start and stop at the actual display area.
- A soft measuring tape works best; if you don't have one, use a string and then measure the string against a ruler.
- The diagonal measurement stays the same across different aspect ratios, so a 27-inch ultrawide and a 27-inch standard monitor have the same diagonal but different widths and heights.
Measuring Width and Height Separately
If you need to know how much desk space a monitor will take up, you'll want to measure the width and height of the screen itself. Measure the width by placing your tape measure horizontally across the screen from the left edge of the display to the right edge, staying within the bezel. Then measure the height vertically from the top of the screen to the bottom.
These measurements matter when you're planning a desk setup, mounting a monitor on a wall, or fitting multiple monitors side by side. The width and height depend on the aspect ratio—a 27-inch ultrawide (21:9) will be much wider than a 27-inch standard monitor (16:9), even though both have the same diagonal size.
Understanding Aspect Ratio and Why It Matters
The aspect ratio is the relationship between the width and height of your screen, written as two numbers like 16:9 or 21:9. This ratio determines the actual shape of your monitor. A 16:9 monitor is wider than it is tall, but not as extremely wide as a 21:9 ultrawide. A 4:3 monitor (older style) is closer to square.
The aspect ratio affects how much horizontal or vertical space you have for work. A 16:9 monitor is standard for most people and works well for web browsing, video, and general computing. A 21:9 ultrawide gives you extra horizontal space, which is useful if you work with spreadsheets, video editing, or want to tile windows side by side. A 16:10 monitor (slightly taller than 16:9) is common in professional work.
You can find your monitor's aspect ratio by checking the product manual, the manufacturer's website, or your computer's display settings. The aspect ratio doesn't change the diagonal measurement—it only changes the width and height proportions.
Measuring the Bezel and Stand Depth
The bezel is the plastic frame around the screen. If you're mounting your monitor on a wall or fitting it into a tight space, you need to know how much space the bezel takes up. Measure from the edge of the screen to the outer edge of the plastic frame on all four sides. Modern monitors often have very thin bezels (sometimes under half an inch), but older monitors can have bezels an inch or more thick.
The stand depth is how far the monitor's base extends forward from the back of the screen. Measure from the wall (or the back of the monitor) to the front edge of the stand. This matters if your desk space is limited or if you're planning to mount the monitor on an arm instead of using the stand. Many monitors have stands that can be adjusted or removed, so check whether you plan to use the original stand or replace it.
Finding Your Monitor's Specifications Online
You don't always have to measure by hand. Most monitor manufacturers publish exact specifications on their websites, including the diagonal size, width, height, bezel thickness, and stand depth. Look up your monitor's model number (usually printed on the back or bottom of the monitor) and search for it on the manufacturer's website or on retail sites like Amazon or Best Buy.
The product manual often includes a diagram with all measurements labeled. If you bought your monitor recently, check your email for a receipt or confirmation—many retailers include a link to the full product specifications. This method is faster and more accurate than measuring by hand, especially if you're trying to match exact dimensions for a replacement monitor.
Measuring Resolution and Pixel Density
Resolution (measured in pixels, like 1920×1080 or 2560×1440) is different from physical size. Two monitors can have the same diagonal size but different resolutions. A 27-inch monitor with 1920×1080 resolution will have larger, blockier pixels than a 27-inch monitor with 2560×1440 resolution. The second one will show sharper text and images because the pixels are packed more densely.
Pixel density is measured in pixels per inch (PPI) and tells you how sharp the image will look. You can calculate it yourself: divide the diagonal resolution in pixels by the diagonal size in inches. For example, a 27-inch monitor with 2560×1440 resolution has roughly 109 PPI. Most people find 100+ PPI sharp enough for comfortable reading and work. Below 90 PPI, text can start to look fuzzy on a desktop monitor.
Resolution is set in your computer's display settings and can usually be changed. Physical size and pixel density cannot be changed—they're fixed properties of the monitor itself.
Common Monitor Sizes and Their Typical Dimensions
| Diagonal Size | Typical Width (16:9) | Typical Height (16:9) | Common Use |
|---|---|---|---|
| 21.5 inches | 19 inches | 11 inches | Budget office work, secondary monitor |
| 24 inches | 21.5 inches | 12 inches | Standard office, gaming, general use |
| 27 inches | 24 inches | 13.5 inches | Professional work, gaming, content creation |
| 32 inches | 28 inches | 16 inches | Large workspace, video editing, design |
These are approximate dimensions for standard 16:9 aspect ratio monitors. Ultrawide monitors (21:9) will be significantly wider but have the same height. The actual width and height can vary slightly between manufacturers, so always check the specific model's specifications if you need exact measurements.
Frequently Asked Questions
Do I measure the monitor with or without the stand?
Measure only the screen itself for the diagonal size—the stand doesn't count. If you need to know how much desk space the monitor takes up, measure the stand depth separately. The diagonal size is always just the screen.
What's the difference between screen size and resolution?
Screen size is the physical diagonal measurement in inches. Resolution is the number of pixels displayed, like 1920×1080. You can have two monitors the same size with different resolutions—the resolution affects sharpness, not the physical dimensions.
Can I use a regular ruler instead of a measuring tape?
A rigid ruler works if your monitor is flat and you can hold it diagonally, but a soft measuring tape is easier and more accurate. If you only have a ruler, use a string instead: lay it diagonally across the screen, mark the corners, and measure the string with your ruler.
Why do monitors list size diagonally instead of width and height?
The diagonal measurement is a single number that's straightforward to compare across different aspect ratios. A 27-inch ultrawide and a 27-inch standard monitor have the same diagonal but very different widths. Manufacturers use diagonal size as the standard because it's consistent and straightforward to advertise.
How do I find my monitor's model number to look up specifications?
The model number is usually printed on a sticker on the back of the monitor, sometimes on the bottom, or occasionally on the front bezel. It's also in your computer's display settings—right-click the desktop, select display settings, and look for the monitor name. You can search that name on the manufacturer's website to find the full specifications.