Screen Resolution Checker: Pixels and Refresh Rate

How to use it

Read Screen (CSS pixels): the size of the whole screen, as the browser counts it.
Compare Screen (physical pixels) with the figure on your display's box or in your system settings. It is the CSS size times the Device pixel ratio.
Check HDR display and Refresh rate. Press Measure again with this tab in front, and close other programs that use the screen.

CSS pixels and physical pixels

A website measures the screen in CSS pixels, a unit of the page rather than of the panel. On a high-density screen one CSS pixel is drawn with several physical pixels: the device pixel ratio says how many along each side. A phone with 390 CSS pixels of width and a ratio of 3 has 1170 physical pixels across.

The browser window is smaller than the screen when it is not maximised. Its size changes live as you resize it, and changes when you zoom, because zooming changes the number of CSS pixels that fit.

Aspect ratio, colour depth and HDR

The aspect ratio is the width divided by the height, reduced to a fraction: 1920 by 1080 is 16:9. Common screens have names: 16:9 and 16:10 are widescreen, 4:3 is the older standard, and 21:9 and 32:9 are ultrawide. When the fraction has large terms, the page shows the nearest common ratio, marked as about.

Colour depth is the number of bits used for each pixel. At 24 bits a screen can show 16,777,216 colours. HDR means the display can show a wider range of brightness and colour; the page reports whether your browser says it has such a display, using the CSS dynamic-range media feature.

The refresh rate

The refresh rate is how many times a second the screen is redrawn: 60 Hz is common, and 120 Hz or 144 Hz on gaming and newer screens. The page counts the animation frames the browser draws over one second and takes the typical gap between them, so a few dropped frames do not change the answer. Browsers do not give the panel's rate directly, so this is a measurement.

Example: a 1080p laptop at 125 percent scaling

A laptop panel of 1920 by 1080 pixels with Windows scaling at 125 percent gives a device pixel ratio of 1.25. The browser then reports a screen of 1536 by 864 CSS pixels, and the physical size is 1920 by 1080 again.

The figures below are what the page shows for that case: the aspect ratio is 16:9 and the screen has about 1.3 megapixels in CSS terms.

Measure	Value
Screen (CSS pixels)	1536 × 864
Screen (physical pixels)	1920 × 1080
Device pixel ratio	1.25
Aspect ratio	16:9 · widescreen
Megapixels	1.3

Frequently asked questions

What is the difference between CSS and physical pixels?

Physical pixels are the dots of the panel. CSS pixels are the unit a web page uses, which the browser maps onto physical pixels using the device pixel ratio. On a high-density screen the CSS size is smaller than the physical size.

Why does my browser say my screen is 1536 pixels wide on a 1920 pixel display?

Windows scaling makes the screen look larger, so it has fewer CSS pixels. At 125 percent scaling, 1920 physical pixels are 1536 CSS pixels; the physical size is still 1920.

What is a good refresh rate?

60 Hz is the usual rate for office and video work. Higher rates, such as 120 Hz or 144 Hz, make motion look smoother for games and scrolling, and many phones switch rates to save battery.

Why does HDR show No on my HDR monitor?

The browser reports HDR only when the operating system and the display both turn it on for the browser, so an HDR monitor may show No when HDR is off in Windows or macOS settings.

Can this page see my monitor's model?

No. It reads only the figures the browser gives: size, pixel ratio, colour depth, orientation and the HDR flag. Model names and serial numbers are not available to web pages.

Is anything about my screen sent to a server?

No. Every figure is read and measured in your browser, and nothing is sent to us or stored.

Sources

Figures and text last checked on Tuesday, November 10, 2026.