What the numbers mean
Screen size is the width and height your computer tells web pages the screen is. MDN says it's counted in CSS pixels, the unit a web page is laid out in. So it's the size things are arranged at, and it can be smaller than the number of dots your display has.
Pixel ratio is how many of the display's own pixels span one CSS pixel, across and down. MDN's page on it says 1 is a classic 96 DPI display and 2 is what to expect from a HiDPI or Retina display. Other numbers happen, and phone screens often give more than 2.
Pixels drawn across is the screen size times the pixel ratio. A computer can draw at less than the display's own resolution, so this isn't always your display's own pixel count. Microsoft's page says monitors can run at lower than their native resolutions, and that text then won't look as sharp.
This browser window is the size of the page area in this window, scroll bar included. It changes when you resize the window, and it isn't your screen.
Why it can differ from your settings
Windows keeps two settings that matter here. In Settings › System › Display, Scale changes the size of text and apps, and Display resolution is the separate row for the resolution itself. Microsoft Learn lists 100%, 125% and 150% as the standard DPI settings. Usually the screen size here is the Display resolution divided by the scale, and the pixel ratio is the scale written as a number: 150% is 1.5.
An example: a Display resolution of 3840 × 2160 at a scale of 150% shows here as a screen size of 2560 × 1440 with a pixel ratio of 1.5.
On a Mac, System Settings › Displays lists the resolutions you can pick. Apple's page says a Mac picks the resolution for the display by itself, and recommends keeping that default.
Where to find the resolution your computer uses
Windows 11. Go to Start › Settings › System › Display. The Display resolution row is there, and Microsoft's page on changing your screen resolution and layout puts Scale in the Scale & layout section of the same page. It says the option marked (Recommended) is usually the one to stick with.
Windows 10. The same place, Start › Settings › System › Display. Scroll to Scale and layout and find Display resolution.
A Mac. Choose Apple menu › System Settings, then click Displays. Apple's page on changing your Mac display's resolution has the rest.
What this page can't tell you
Your display's own pixel count. It can only multiply what the browser gives it.
Inches. A screen tells a page its widths, heights, colour depth and orientation, and no physical size. So this page can't say whether you have a 13-inch or a 27-inch screen.
Refresh rate. It isn't in that list either.
Which screen, if you have more than one. The browser reports the screen that has the middle of this window on it, MDN says.
Zooming the page changes the pixel ratio: MDN says zooming in raises it, and pinch-zooming doesn't. Set your browser's zoom back to 100% to see your system's own.
Captures from a sharp screen
VizShot has one setting that touches on this. Save Retina captures at half size in Settings › Images saves sharp-screen captures at half the pixels, for smaller files. On Windows it's called "high-resolution captures". It's off by default, and the clipboard always gets the full-size PNG. File names and formats has the details, and you can download VizShot.
Questions
Is screen resolution the same as display resolution?
On this page they mean the same thing, the width and height in pixels. Windows calls its setting Display resolution, and Apple's page calls it the display's resolution.
Why does it say 2560 × 1440 when my monitor is 4K?
Probably because of scale. If your Display resolution is 3840 × 2160 and your scale is 150%, you would usually see 2560 × 1440 here at a pixel ratio of 1.5. Check Settings › System › Display, as above.
Why did the pixel ratio change when I zoomed?
Page zoom changes it. MDN says zooming in raises the ratio. It can also change when you drag the window to a screen with a different pixel density.
Does it work on a phone?
Yes. The page reads the same numbers, and phone screens often give a pixel ratio above 2. If your browser gives no pixel ratio, the page says so and shows the rest.
Why does my screenshot have more pixels than my screen size?
Why a Retina screenshot is too big goes through it.
Is anything sent anywhere?
No. The page reads a few numbers from your browser and shows them.
Checked against
- MDN: Window devicePixelRatio property, read 15 October 2026
- MDN: Screen, read 15 October 2026
- Microsoft Learn: DPI and device-independent pixels, read 15 October 2026
- Microsoft: Change your screen resolution and layout in Windows, read 15 October 2026
- Apple: Change your Mac display's resolution, read 15 October 2026