The Screen Resolution & Aspect Ratio Checker detects your display’s resolution and tells you its aspect ratio, total megapixels and the named standard it matches. You can also type any width and height to identify the ratio of a different screen or image — all in your browser.
What it detects
On load, the tool reads your screen’s width and height and multiplies by your device pixel ratio to report physical pixels — the true resolution behind the CSS pixels a page normally sees. It then reduces those numbers to an aspect ratio.
How the aspect ratio is calculated
The width and height are divided by their greatest common divisor to reduce the ratio to lowest terms, then matched against the common standards:
| Resolution | Ratio | Standard | Common use |
|---|---|---|---|
| 1920×1080 | 16:9 | Full HD | Most monitors and TVs |
| 3840×2160 | 16:9 | 4K UHD | High-end displays, streaming |
| 2560×1600 | 16:10 | WUXGA-class | Laptop screens |
| 2560×1440 | 16:9 | QHD / 2K | Gaming monitors |
| 3440×1440 | 21:9 | Ultrawide | Cinematic desktop use |
| 2048×1536 | 4:3 | XGA-class | Older monitors, some tablets |
| 2388×1668 | 7:5 | iPad Pro 11” | Apple tablet displays |
| 2556×1179 | Approx. 19.5:9 | iPhone 15 Pro | Modern smartphone |
The decimal value (width divided by height) lets you compare displays even when the integer ratios look different — for example, 16:9 = 1.777 and 16:10 = 1.600.
Why this matters
Video production — knowing your display ratio lets you confirm that a video exported in 16:9 will not be pillarboxed or letterboxed on your screen. If your monitor is 21:9 and your export is 16:9, you will see black bars on the sides.
Web and app development — responsive design breakpoints are usually written in CSS pixels, but a Retina or high-DPI screen has a device pixel ratio of 2 or 3. A 1440×900 laptop at 2× DPR has a physical resolution of 2880×1800. Knowing both values helps when targeting @2x image assets and srcset values.
Image resizing — paste any image dimension into the fields to check whether it has a standard ratio before cropping. A 1200×800 image reduces to 3:2, for example, which is a standard still-photography ratio.
Screenshot analysis — if a screenshot appears stretched or squashed, check its actual pixel dimensions here. A 1280×800 image is 8:5 (≈16:10), not 16:9, so filling a 16:9 container will distort it.
Understanding megapixels
Megapixels is simply width × height ÷ 1,000,000. A 1920×1080 display has about 2.07 megapixels; a 4K display at 3840×2160 has about 8.29 megapixels — four times as many pixels in the same screen area. For photography, a 24-megapixel sensor at 6000×4000 pixels gives you much more cropping flexibility than an 8-megapixel phone camera at 3264×2448.
Everything is read and calculated locally in your browser — nothing is uploaded.