Measure diagonally from corner to corner to find your monitor's screen size

A monitor's size is measured diagonally across the screen from one corner to the opposite corner, in inches. This is the number you see in product listings — a "27-inch monitor" means the distance from the bottom-left corner to the top-right corner is 27 inches. The measurement includes only the visible screen area, not the plastic bezel or stand.

To measure your own monitor, use a tape measure or ruler and place it at the bottom-left corner of the screen. Pull it diagonally toward the top-right corner and read the number where it ends. If you are measuring a monitor that is currently mounted on a wall or arm, you may need to measure carefully to avoid hitting the mount itself — measure only the glass or screen surface.

If you cannot measure physically, you can find the screen size in your monitor's manual or by searching the model number on the manufacturer's website. The model number is usually printed on the back of the monitor or on a sticker underneath.

Key Takeaways

  • Monitor size is always measured diagonally across the screen in inches, from corner to corner.
  • The measurement includes only the visible screen area, not the frame or stand around it.
  • You can find the screen size in your monitor's manual or by looking up the model number online if you cannot measure it yourself.
  • Width and height measurements are separate from screen size and depend on the monitor's aspect ratio.
  • Knowing your monitor's exact dimensions helps when choosing a desk, mount, or replacement screen.

Understanding aspect ratio and how it affects width and height

Screen size alone does not tell you how wide or tall your monitor is. A 27-inch monitor with a 16:9 aspect ratio (the most common shape) will have different width and height than a 27-inch monitor with a 21:9 ultrawide aspect ratio. The aspect ratio is the proportion of width to height.

A 16:9 monitor is wider than it is tall, but not extremely so. A 21:9 monitor is much wider and shorter, designed for watching films or working with multiple windows side by side. A 4:3 monitor (older style) is nearly square. If you need to know the exact width and height of your monitor, you will need both the screen size and the aspect ratio.

You can find the aspect ratio in your monitor's manual or specifications sheet. It is often printed on the box or listed on the manufacturer's website next to the model number.

How to find width and height if you know the screen size and aspect ratio

If you have the diagonal measurement and the aspect ratio, you can calculate the width and height using basic math. For a 16:9 monitor, multiply the diagonal by 0.87 to get the width, and multiply the diagonal by 0.49 to get the height. For a 21:9 monitor, multiply the diagonal by 0.96 for width and 0.41 for height.

For example, a 27-inch monitor with 16:9 aspect ratio would be roughly 23.5 inches wide and 13.2 inches tall. These are approximate because the actual measurements depend on how much of the diagonal the screen itself takes up versus the bezel.

If you need exact measurements for mounting or desk planning, measure the monitor directly rather than relying on calculations. Place your ruler or tape measure along the edge of the screen from the leftmost point to the rightmost point for width, and from the top to the bottom for height.

Measuring the monitor's footprint for desk space and mounting

The footprint is the total space the monitor takes up on your desk, including the stand. Measure the width of the monitor from the leftmost edge of the stand to the rightmost edge. Then measure the depth from the front of the screen to the back of the stand. These measurements tell you whether the monitor will fit on your desk or shelf.

If you plan to mount the monitor on an arm or wall bracket, you need to know the VESA mounting pattern. This is the distance between the four screw holes on the back of the monitor, measured in millimeters. Common VESA patterns are 75×75 mm (smaller monitors) and 100×100 mm (larger monitors). Check your monitor's manual or the back of the monitor itself for the VESA pattern before buying a mount.

The height of the stand also matters if you have limited vertical space or want to position the monitor at eye level. Measure from the desk surface to the top of the screen when the monitor is sitting in its normal position.

Finding monitor specifications if you cannot measure physically

If your monitor is difficult to access or you need the information quickly, the easiest way is to look up the model number. The model number is usually on a sticker on the back of the monitor, sometimes near the power cable connection. Write down the full model number exactly as it appears.

Search the model number on the manufacturer's website — Dell, LG, ASUS, HP, and other brands all have searchable product databases. The product page will list the screen size, aspect ratio, width, height, depth, weight, and VESA mounting pattern. You can also find this information in the user manual, which is usually available as a PDF read on the same page.

If you have lost the manual and cannot find the model number, try searching "monitor specifications" plus any text you can see on the monitor itself, such as the brand name or any visible numbers. Manufacturer support chat or phone lines can also look up your monitor's specs if you provide the model number.

Why monitor measurements matter for your setup

Knowing your monitor's exact size and dimensions helps you plan your workspace. If you are buying a new desk, you need to know whether your monitor will fit. If you are mounting the monitor on an arm or wall bracket, you need the VESA pattern and weight to choose a compatible mount. If you are replacing a monitor, knowing the current size helps you decide whether to buy the same size or go larger.

Monitor size also affects how much desk space you have left for a keyboard, mouse, and other items. A larger monitor takes up more room but may reduce eye strain if you sit far from your screen. A smaller monitor saves space but may be harder to read if you have vision difficulties.

Measuring your current setup also helps when troubleshooting display problems. Some issues are caused by the monitor being too far away or at the wrong angle, and knowing the exact distance and dimensions can help you adjust your seating position or monitor height.

Common monitor sizes and their typical dimensions

Most desktop monitors fall into a few standard sizes. A 24-inch monitor with 16:9 aspect ratio is roughly 21 inches wide and 12 inches tall. A 27-inch monitor with 16:9 is roughly 23.5 inches wide and 13.2 inches tall. A 32-inch monitor with 16:9 is roughly 28 inches wide and 15.7 inches tall.

Ultrawide monitors are less common but growing in popularity. A 34-inch ultrawide with 21:9 aspect ratio is roughly 32.5 inches wide and 13.7 inches tall — much wider than a standard 27-inch but not much taller. These dimensions are approximate and vary slightly between manufacturers and models.

Older monitors with 4:3 aspect ratio are nearly square. A 19-inch 4:3 monitor is roughly 15 inches wide and 11 inches tall. These are less common in new purchases but you may encounter them in older setups or offices.

Frequently Asked Questions

Does the monitor size include the plastic frame around the screen?

No. The screen size measurement is only the visible display area, from corner to corner of the actual screen. The plastic bezel or frame around the edge is not included in the measurement. When you measure diagonally, measure only the glass or screen surface itself.

What is VESA and why do I need to know it?

VESA is the standard mounting pattern for monitor arms and wall brackets. It is the distance between the four screw holes on the back of your monitor, measured in millimeters. Common sizes are 75×75 mm and 100×100 mm. You need to know your monitor's VESA pattern to buy a compatible mount or arm.

Can I measure my monitor with my phone instead of a tape measure?

Some phone measurement apps use the camera to estimate distances, but they are less accurate than a physical tape measure or ruler, especially over longer distances. If you use a phone app, measure twice to confirm the result. A tape measure or ruler is more reliable for monitor measurements.

Where do I find the model number on my monitor?

The model number is usually on a sticker on the back of the monitor, often near the power cable connection or the VESA mounting holes. It may also be printed on the bottom of the stand or on the original box. Once you have the model number, search it on the manufacturer's website to find all the specifications.

Does a larger monitor always mean a wider desk space?

Not necessarily. A 27-inch ultrawide monitor may be wider than a 32-inch standard monitor, depending on the aspect ratio. A 21:9 ultrawide is much wider but shorter than a 16:9 standard monitor of the same diagonal size. Measure the width and depth of the monitor itself, not just the screen size, to know how much desk space it will use.