Aspect ratio calculator
The ratio of any width and height, or the missing side for 16:9, 4:3, 4:5 and the rest, with a table of standard sizes.
What is my screen resolution?
Your screen resolution, the scaled size websites see, your browser window and pixel ratio, read from this device as the page opens.
- Open this page on the device you want to check
- Read your screen, window and pixel ratio
- Resize the window and watch it update
Your screen resolution
- Known as
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- Scaled size (CSS pixels)
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- Browser window
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- Pixel ratio
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- Aspect ratio
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- Orientation
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- Colour depth
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The calculator needs JavaScript. The formula is below if you would rather work it out by hand.
Kept results
Kept in this browser only. Nothing is sent to us.
This screen resolution checker reads your screen the moment the page opens. At the top is your physical resolution, the pixels your screen actually has. Underneath are the scaled size websites see, your browser window, your pixel ratio and your screen’s aspect ratio. Resize the window and it updates as you go.
What your screen resolution means
Resolution is the number of pixels across and down. 1920 × 1080 means 1,920 pixels wide and 1,080 high, just over two million in all.
More pixels on the same size of screen means sharper text and images. More pixels on a bigger screen can mean the same sharpness, just larger. That’s why resolution alone doesn’t tell you how good a screen looks.
Why is my resolution showing smaller than my screen?
Scaling. A laptop with a 1920 × 1080 screen often runs at 125% or 150% in Windows, so text isn’t tiny. Macs with Retina screens run at 2x. The browser then works in larger “CSS pixels”: at 125%, that 1920 × 1080 screen reports 1536 × 864 to websites.
Both numbers are real. The first is what the screen draws; the second is the space a website lays itself out in. This page shows you both.
How to check your screen resolution on Windows and Mac
On Windows 11, open Settings, then System, then Display, and look at Display resolution. The Scale setting just above it is the scaling that explains the difference.
On a Mac, open the Apple menu, then System Settings, then Displays. Macs describe the resolution as a “looks like” size, which is the scaled size in this page’s second figure.
Common screen resolutions
| Resolution | Known as |
|---|---|
| 1280 × 720 | HD, 720p |
| 1366 × 768 | HD, common on older laptops |
| 1920 × 1080 | Full HD, 1080p |
| 2560 × 1440 | QHD, 1440p |
| 3840 × 2160 | 4K UHD |
What screen resolution should a website be designed for?
All of them. People visit on phones held upright, laptops at 125%, wide monitors and everything between, and they resize windows as they go. A site built for one resolution looks wrong on most of the others.
Good sites are designed in ranges, with the layout changing at set window widths, and then tested on real devices. It’s how we build every site; see our web design work, or use the aspect ratio calculator and px to rem converter for your own build.
A website is judged by what it converts, not by what it wins.
Client results, measured in the numbers the business cares about.
See the workQuestions people ask.
How do I find out my screen resolution?
This page reads it the moment it opens. To see it in your settings: on Windows 11, Settings, then System, then Display, and look at Display resolution; on a Mac, the Apple menu, then System Settings, then Displays.
How do I know if my screen is 1080p or 1440p?
Look at the physical resolution at the top of this page. 1920 × 1080 is 1080p, 2560 × 1440 is 1440p and 3840 × 2160 is 4K.
What is the screen size for a 1920 × 1080 resolution?
Resolution doesn't tell you the size. 1920 × 1080 is used on 13-inch laptops and 27-inch monitors alike; screen size is the diagonal measured in inches, and the same pixels simply spread further on a bigger screen.
Why is my resolution showing smaller than my screen?
Scaling. Windows often runs at 125% or 150% and Macs at 2x on Retina screens, so the browser works in larger "CSS pixels" to keep text readable. This page shows both: the physical pixels your screen has, and the scaled size websites see.
Which size matters when designing a website?
The browser window, in CSS pixels. That is what a site's layout responds to, and it changes as people resize windows or turn phones sideways. Good sites are designed to work across the whole range, not for one resolution.
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