What Is My Screen Size?
Your screen resolution, browser viewport, device pixel ratio, aspect ratio, and color depth — detected live, no install. You can even measure your screen's true physical size in inches. Checking your display's smoothness? Try the Refresh Rate Tester.
Everything is read live in your browser — resize the window and the viewport updates.
Measure your physical screen size
Browsers can't read your screen's physical size, so calibrate it: hold a standard credit or bank card against the screen and drag the slider until the box below is exactly the same width. That gives your true pixel density and screen size.
Estimate — accuracy depends on matching the card width precisely and your display scaling.
Resolution vs viewport vs physical pixels
Three numbers often get confused. Screen resolution is what your display reports in CSS pixels. The viewport is the smaller area your browser draws into, after tabs and toolbars — it shrinks the instant you resize the window. And the physical resolutionis the panel's real pixel count, which equals the reported resolution times your device pixel ratio on high-density screens.
Why your numbers might surprise you
If the resolution here looks lower than your monitor's spec, it's almost always display scaling— at 125% or 150% your OS reports a smaller logical resolution so everything looks bigger, while the panel's real pixels are unchanged. Multiply by the device pixel ratio, or check the physical resolution above, to see the panel's native pixel count. Browser zoom affects the viewport and pixel ratio too, so reset it to 100% for true readings.
Test more of your display
Now you know its size, check how your screen performs: detect its refresh rate, hunt for dead pixels, check for backlight bleed, or measure your real frame rate.
Frequently asked questions
What is my screen resolution?
Your screen resolution is the number of pixels your display reports, written as width × height — and it's shown in big numbers at the top of this page, detected automatically from your browser. Common resolutions are 1920 × 1080 (Full HD), 2560 × 1440 (QHD), and 3840 × 2160 (4K). The figure your browser reports is in CSS pixels; on a high-density screen the true physical pixel count is that number multiplied by your device pixel ratio, which is also shown here.
What's the difference between screen resolution and viewport size?
Screen resolution is the full size of your display, while the viewport is just the area your browser actually draws the page into — your screen minus the tabs, address bar, bookmarks bar, and any scrollbars. That's why the viewport is always smaller than your screen, and why it changes the moment you resize the browser window while the screen resolution stays the same. Web designers care about the viewport because that's the space a website has to work with.
What is device pixel ratio (DPR)?
Device pixel ratio is how many physical pixels your screen packs into each CSS 'pixel' that web pages are measured in. A normal monitor has a DPR of 1, while high-density 'Retina' laptops and phones use 2 or 3, drawing two or three real pixels for every CSS pixel to look sharper. That's why your browser might report 1512 × 982 on a laptop whose panel is actually 3024 × 1964 — multiply the reported resolution by the DPR to get the true physical pixel count.
Why is my resolution lower than my monitor's native resolution?
Two common reasons. First, display scaling: at 125% or 150% scaling, your operating system reports a smaller logical resolution so text and icons appear larger, even though the panel's physical pixels haven't changed. Second, you may simply have a non-native resolution selected in your display settings, which looks softer than native. To see your true panel resolution, check the physical resolution shown here, or set scaling to 100% in your OS display settings.
How do I find my screen's physical size in inches?
Browsers can't read a screen's physical dimensions, only its pixels, so this page lets you calibrate: hold a standard credit or bank card against the screen and drag the slider until the on-screen box matches its width. Because every ID-1 card is exactly 85.6 mm wide, that gives your real pixel density (PPI), which the tool combines with your pixel count to estimate your diagonal screen size and physical width and height. It's an estimate, but a close one when you match the card carefully.
How do I change my screen resolution?
On Windows, right-click the desktop, choose Display settings, and pick a resolution from the Display resolution menu — the one marked 'Recommended' is your panel's native resolution. On macOS, open System Settings → Displays and choose Default for your display or select a scaled option. For the sharpest image, always use the native resolution and adjust the scaling level rather than dropping to a lower resolution.