Calculate an aspect ratio
Calculate aspect ratios, keep proportions when resizing and copy the CSS. Presets for 16:9, 4:3, 1:1, 9:16, ultrawide and social formats. Free.
- Files never leave your device
- Free, no sign-up
- No watermark
About Aspect Ratio Calculator
Find the aspect ratio of any width and height, or work out the missing dimension when you resize. Enter both sides to get the simplified ratio, lock it, then change one side and the other updates automatically. Presets cover widescreen 16:9, standard 4:3, square 1:1, vertical 9:16, ultrawide and photo formats, and the tool gives you ready-to-copy CSS. It is all calculated in your browser.
How to use Aspect Ratio Calculator
- 1
Enter a width and height to see the ratio.
- 2
Lock the ratio to keep proportions.
- 3
Change one dimension and the other is calculated.
- 4
Copy the CSS output or pick a preset.
Why use this tool
- Simplifies any size to its ratio, such as 1920×1080 to 16:9.
- Ratio lock for proportional resizing.
- Presets for video, photo and social formats.
- Copyable CSS aspect-ratio output.
- Visual preview of the shape.
Frequently asked questions
It is the relationship between width and height, written as width:height. 1920×1080 and 1280×720 are both 16:9.
16:9, for example 1920×1080. Shorts and Reels use vertical 9:16.
Add aspect-ratio: 16 / 9 to an element and its height adjusts to its width automatically.
No. It calculates sizes. Use Resize Image to change an image to the dimensions you found.
Yes. There is no account, no watermark and no usage limit. The tool runs in your own browser, so there is no server cost to charge you for.
Yes. It runs in any modern browser on Android and iOS as well as on Windows, macOS and Linux, with nothing to install.
It simplifies to 4:5, the portrait size used for Instagram posts.
No. Calculations run in your browser and nothing is saved or sent anywhere.
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