Measure screen size diagonally from corner to corner

Screen size is always measured diagonally—from the bottom-left corner to the top-right corner (or vice versa)—in inches. This diagonal measurement is what manufacturers list as the screen's size, whether it's 24 inches, 27 inches, or 32 inches. You're measuring the actual display area, not the bezel (the plastic or metal frame around the screen).

Use a measuring tape or ruler and place it at one corner of the screen glass itself. Pull it straight across to the opposite corner. Write down the measurement in inches. If your tape measure shows centimeters, divide by 2.54 to convert to inches. Most people round to the nearest whole number—a screen that measures 23.8 inches is typically called a 24-inch monitor.

The diagonal measurement matters because two screens with the same width can have different heights depending on their aspect ratio (the relationship between width and height). A 16:9 widescreen monitor and a 4:3 older monitor with the same width will have different diagonal measurements and different screen sizes.

Key Takeaways

  • Screen size is measured diagonally across the glass display area in inches, not the width or height alone.
  • Resolution is the number of pixels displayed horizontally and vertically, found in your operating system's display settings rather than measured with a tool.
  • Aspect ratio describes the relationship between width and height, with 16:9 being the most common for modern monitors.
  • Refresh rate (measured in hertz) is separate from screen size and resolution, and controls how many times per second the image updates.

Find your screen resolution in Windows display settings

Resolution is not something you measure with a tape—it's a specification built into your monitor and operating system. On Windows, right-click on an empty area of your desktop and select Display settings. Scroll down to the Display resolution section. You'll see two numbers listed, like 1920 × 1080 or 2560 × 1440. The first number is the horizontal pixel count, and the second is the vertical pixel count.

If you don't see Display settings in the right-click menu, open the Settings app (press the Windows key and type "Settings"), then go to System and select Display from the left sidebar. The resolution appears under the preview of your monitor.

Your monitor may support multiple resolutions, but Windows will default to the one that matches your screen's native resolution—the resolution it was designed for. Changing the resolution in settings changes how large text and icons appear on your screen, but it doesn't change the physical screen size.

Check resolution on Mac in System Preferences

On a Mac, click the Apple menu in the top-left corner and select System Settings (or System Preferences on older versions). Click Displays in the sidebar. You'll see a Resolution section showing options like 1920 × 1200 or 2560 × 1600. The currently selected resolution is your active display setting.

If you see a dropdown menu labeled Scaled, your Mac is using a scaled resolution rather than the native one. Click the dropdown to see other available resolutions. The option labeled "Default for display" is usually the native resolution your monitor was designed for.

Understand aspect ratio and how it affects screen shape

Aspect ratio is the proportion of width to height, written as two numbers separated by a colon. The most common aspect ratio for modern computer monitors is 16:9 (widescreen), which means for every 16 units of width, there are 9 units of height. Other common ratios include 16:10 (slightly taller than 16:9) and 4:3 (older, more square-shaped screens).

You can calculate aspect ratio from your resolution. Take your horizontal pixel count and divide it by your vertical pixel count, then simplify. A 1920 × 1080 resolution divides to 16:9. A 2560 × 1440 resolution also simplifies to 16:9. A 1920 × 1200 resolution simplifies to 16:10.

Aspect ratio matters when you're choosing a monitor for specific work. Video editors often prefer 16:9 because that matches standard video formats. Programmers sometimes prefer 16:10 or even ultrawide monitors (21:9) for extra horizontal space. Knowing your screen's aspect ratio helps you understand how content will fit on your display.

Locate refresh rate in advanced display settings

Refresh rate is how many times per second your monitor redraws the image on screen, measured in hertz (Hz). A 60 Hz monitor refreshes 60 times per second. Gaming monitors often have 144 Hz, 165 Hz, or higher refresh rates. This is separate from screen size and resolution.

On Windows, open Display settings, scroll down, and click Advanced display settings. At the bottom, you'll see Refresh rate with a dropdown menu showing options like 60 Hz or 144 Hz. The number shown is your current refresh rate.

On Mac, open System Settings, click Displays, then click Refresh rate to see available options. Most Mac displays default to 60 Hz unless you have a newer high-refresh monitor.

Check your monitor's specifications on the manufacturer's website

If you want to confirm all your screen's specifications at once, look up the monitor model number. You can usually find this on a sticker on the back of the monitor, or in your computer's system information. Search for "[Brand] [Model Number] specifications" online to find the manufacturer's official specs sheet.

The specs sheet will list the screen size in inches, native resolution, aspect ratio, refresh rate, and other details like brightness and contrast ratio. This is useful if you're troubleshooting a display problem or trying to match your monitor with compatible cables or adapters.

If you've lost the model number, you can also open your system information. On Windows, press Windows key + Pause/Break, or search "System Information" in the Start menu. On Mac, click the Apple menu and select About This Mac, then click System Report. Look for a section labeled "Displays" that may show the monitor model.

Frequently Asked Questions

What's the difference between screen size and resolution?

Screen size is the physical diagonal measurement of your monitor in inches. Resolution is the number of pixels displayed on that screen. You can have two 24-inch monitors with the same size but different resolutions—one might be 1920 × 1080 and another 2560 × 1440. The second one will show more detail because it has more pixels packed into the same physical space.

Why does my resolution look different from what the settings say?

Windows and Mac both offer scaled resolutions, which means the operating system is displaying a lower resolution and enlarging it to fit your screen. This makes text and icons larger and easier to read, but uses fewer of your monitor's actual pixels. Check your Display settings for a "Scaled" or "Resolution" dropdown to see if a scaled option is selected instead of the native resolution.

Can I change my screen size?

No. Screen size is a physical property of your monitor and cannot be changed through software. You can change resolution, which makes content appear larger or smaller, but that's different from changing the actual screen dimensions. If you need a larger screen, you need a different monitor.

Is a higher refresh rate better?

A higher refresh rate (like 144 Hz instead of 60 Hz) produces smoother motion and is noticeable during gaming or fast-paced video. For everyday tasks like web browsing and document editing, 60 Hz is sufficient. Higher refresh rates require a more powerful graphics card to take advantage of them, so the benefit depends on what you're doing.

How do I know if my monitor is 16:9 or 16:10?

Look at your resolution in Display settings. Divide the first number by the second. A 1920 × 1080 resolution is 16:9 (1920 ÷ 1080 = 1.78, which is 16 ÷ 9). A 1920 × 1200 resolution is 16:10 (1920 ÷ 1200 = 1.6, which is 16 ÷ 10). You can also measure the width and height with a ruler and divide width by height to get the same answer.