What aspect ratio is my monitor?
Your monitor's aspect ratio is its width divided by its height, reduced to the smallest whole numbers. Divide both sides of the resolution by their greatest common divisor: 1920 x 1080 becomes 16:9, 2560 x 1600 becomes 16:10, and 3440 x 1440 becomes 43:18, which is sold as 21:9. The checker above reports your resolution so you can reduce it.
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- what ratio is my monitor
- what's my aspect ratio
- how to find my screen ratio
- my display aspect ratio
Do it here: What Is My Screen Resolution?
Check your screen resolution, browser viewport, device pixel ratio, colour depth and GPU.
- The method
- Divide width and height by their greatest common divisor
- 1920 x 1080
- Divide both by 120, giving 16:9
- 3440 x 1440
- Divide both by 80, giving 43:18, marketed as 21:9
- Scaling
- Display scaling and browser zoom do not change the ratio
Working it out by hand
- Read the resolution from the checker above, for example 1920 x 1080.
- Find the greatest common divisor of the two numbers. For 1920 and 1080 it is 120.
- Divide both sides by it: 1920 / 120 = 16 and 1080 / 120 = 9, so the ratio is 16:9.
If the arithmetic is awkward, the GCD calculator will reduce the pair for you, and the aspect ratio calculator will do the whole thing including scaling a target size to match.
Common resolutions and their true ratios
| Resolution | Aspect ratio | Usually called |
|---|---|---|
| 1024 x 768 | 4:3 | XGA, legacy displays |
| 1280 x 720 | 16:9 | 720p |
| 1920 x 1080 | 16:9 | 1080p, Full HD |
| 2560 x 1440 | 16:9 | 1440p, QHD |
| 3840 x 2160 | 16:9 | 4K UHD |
| 1920 x 1200 | 16:10 | WUXGA |
| 2560 x 1600 | 16:10 | Common on 13 to 16 inch laptops |
| 2256 x 1504 | 3:2 | Surface-style productivity panels |
| 2560 x 1080 | 64:27 | Ultrawide, sold as 21:9 |
| 3440 x 1440 | 43:18 | Ultrawide, sold as 21:9 |
| 5120 x 1440 | 32:9 | Super ultrawide |
Why an ultrawide sold as 21:9 is not 21:9
21:9 is a marketing label, not an arithmetic one. Reduce 3440 x 1440 and you get 43:18, or about 2.389:1. Reduce 2560 x 1080 and you get 64:27, or about 2.370:1. Neither equals 21 divided by 9, which is about 2.333:1. The label exists because "21:9" sits neatly beside "16:9" on a spec sheet, and because both panels are near enough to the 2.39:1 cinema scope ratio to show a scope film with thin bars.
What scaling does and does not change
Windows display scaling, macOS Retina scaling and browser zoom all change the pixel numbers a browser reports, because they change the size of a CSS pixel. They divide both sides by roughly the same factor, so the ratio is unchanged. The one thing to watch for is rounding: at 150% scaling a 2560 x 1440 panel can report 1707 x 960, which reduces to 1707:960 rather than 16:9. Round to the nearest sensible pair, or reset zoom to 100% before reading.
Where the ratio actually matters
- Wallpapers. A 16:9 image on a 21:9 panel is either stretched or pillarboxed.
- Video export. Exporting 16:9 for an ultrawide leaves side bars; exporting to the panel ratio does not.
- Screen recording. Recording an ultrawide desktop and uploading it to a 16:9 platform adds letterboxing on top of the recording.
- Presentations. Slide decks default to 16:9, which is why they show bars on a 16:10 laptop.
Related tools
- What is my screen size in pixels explains the numbers this ratio is derived from.
- Aspect ratio calculator scales a width or height while holding the ratio.
- Image cropper crops an image to a fixed ratio.
- Image resizer resizes to an exact pixel target.