What Is My Screen Resolution?

About the What Is My Screen Resolution?

See your screen’s resolution as soon as the page opens — in physical pixels and in the CSS pixels web pages use — with the device pixel ratio that links the two, the size of your browser window (the viewport), the screen area left after the taskbar or dock, and the aspect ratio and orientation. The page also reports colour depth, colour gamut (sRGB, Display P3 or Rec. 2020) and whether the browser reports HDR, and it measures the refresh rate by counting the frames the browser draws.

Enter the screen’s diagonal to get its pixel density (PPI), the size of one pixel and its real width and height in centimetres and inches — or type any other resolution and size to compare monitors before you buy one.

Common uses

• Answering “what resolution is my screen?” for a support desk, a game setting or a wallpaper.
• Checking that a new monitor runs at its native resolution and full refresh rate.
• Web developers checking the viewport, device pixel ratio and colour gamut of a device.
• Comparing the pixel density and real size of monitors or laptops before buying.

Physical pixels, CSS pixels and the device pixel ratio

A screen’s physical pixels are the dots it is made of: 1920 × 1080 on a Full HD screen. Web pages are laid out in CSS pixels instead, so that text is a readable size on every screen. The device pixel ratio is how many physical pixels make one CSS pixel: 1 on a basic monitor at 100 % scaling, 1.25 or 1.5 on a Windows laptop with scaling turned up, 2 on a Mac Retina screen and often 2.5 to 3.5 on phones.

The page multiplies the screen size in CSS pixels by that ratio to get the physical resolution. Page zoom is part of the ratio as well (W3C CSSOM View), so zooming in makes the CSS figures smaller and the ratio bigger — keep the zoom at 100 % for exact figures. Pinch zoom on a phone does not change it.

Screen, available area and viewport

• Screen — the whole display, in CSS pixels.
• Available screen area — the screen without the taskbar, the dock or the phone’s system bars.
• Viewport — the inside of the browser window where the page is drawn, scroll bar included; without the scroll bar it can be a little narrower, which the page also shows. This is the size web designers mean by “breakpoints”.

On phones and tablets the figures swap when you turn the device; iPhones and iPads report the screen upright whichever way they are held, so the page turns it the way the device is held.

Colour depth, colour gamut and HDR

• Colour depth is the number of bits per pixel the browser reports: 24 means 8 bits for each of red, green and blue, about 16.7 million colours, and 30 means 10 bits each. Browsers report 24 when they do not know or do not tell, so a 10-bit screen often shows 24 too.
• Colour gamut — the range of colours the screen and browser can show — comes from the color-gamut media feature (W3C Media Queries 4): sRGB for most screens, Display P3 for many recent phones, Macs and wide-gamut monitors, Rec. 2020 for a few high-end displays.
• HDR comes from the dynamic-range media feature (W3C Media Queries 5): “Yes” means the browser reports that the screen can show high dynamic range. The feature tells what the screen can do, not whether an HDR mode is on; some systems report HDR only while it is switched on in their display settings.

How the refresh rate is measured

Browsers draw a page in step with the screen and call the page once per frame (requestAnimationFrame). The page counts those frames for 1.5 seconds and takes the typical interval between them: 16.7 ms is 60 Hz, 6.9 ms is 144 Hz. A result within 2.5 % of a usual rate (60, 75, 120, 144, 165, 240 Hz …) is shown as the nearest one, so 59.94 Hz reads 60 Hz.

The measurement is the rate at which the browser draws, which can be lower than the screen’s: Safari often runs pages at 60 frames a second, battery-saving modes lower it, a variable-refresh screen may slow down when nothing moves, and background tabs are paused. Move the window to the screen you want to measure and press Measure refresh rate again.

Pixel density and physical size

Pixel density is the number of pixels across the diagonal divided by the diagonal: PPI = √(width² + height²) ÷ diagonal in inches. Width and height follow from the same triangle: width = diagonal × width in pixels ÷ √(width² + height²). The pixel size (dot pitch) is 25.4 mm ÷ PPI.

“Pixels blend beyond” is the distance at which one pixel looks 1 arcminute wide — the detail a person with 20/20 vision can just make out: 1 ÷ (PPI × tan 1′). Sit farther away and you can no longer pick out single pixels.

Common screen resolutions

• 1280 × 720 — HD (720p), 16:9
• 1366 × 768 — budget laptops, about 16:9
• 1920 × 1080 — Full HD (1080p), 16:9
• 1920 × 1200 — WUXGA, 16:10
• 2560 × 1440 — QHD (1440p), 16:9
• 2560 × 1600 — WQXGA, 16:10
• 3440 × 1440 — ultrawide QHD, sold as 21:9
• 3840 × 2160 — 4K UHD, 16:9
• 5120 × 2880 — 5K, 16:9
• 7680 × 4320 — 8K UHD, 16:9

Limitations

• The physical resolution is worked out from what the browser reports (CSS pixels × device pixel ratio), so a page zoom other than 100 % and the rounded CSS size of phones can make it a few pixels off.
• Browsers do not tell web pages how big the screen is in centimetres or inches, so pixel density needs the diagonal from you.
• Privacy settings such as Firefox’s fingerprinting resistance, the Tor Browser or Brave’s fingerprint protection may report a standard or rounded screen size instead of the real one.
• With several monitors the page shows the one the browser window is on.
• The refresh rate is the rate the browser draws pages, which can be lower than the screen’s own rate.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.