Developer tools
Aspect ratio calculator
Lock a ratio like 16:9, then type a width or a height and the missing side is solved for you. Tap a preset to switch ratios in one click. Everything runs in your browser - nothing is uploaded.
How it works
Resize something to a fixed aspect ratio without distorting it. Lock a ratio - 16:9, 4:3, 1:1, or any custom pair - then type either the width or the height and the tool solves the other side so the proportions stay exactly the same. It is the everyday maths behind fitting a video, an image, or a layout into a new size while keeping it from stretching or squashing.
The ratio itself is reduced to its simplest whole-number form, so entering 1920 by 1080 tells you the ratio is 16:9, and the common presets are one click away. Change the locked ratio and the height recalculates from the current width; change a dimension and its partner follows. Everything runs in your browser as plain arithmetic, with nothing uploaded.
Example. Lock the ratio to 16:9 and type 1280 into the width box, and the height fills in as 720. Type 1080 into the height instead and the width becomes 1920. Enter an arbitrary size like 800 by 600 and the ratio simplifies to 4:3.
FAQ
What is an aspect ratio?
An aspect ratio is the proportion between something's width and its height, written as two numbers separated by a colon, such as 16:9. It describes shape rather than size: every 16:9 rectangle has the same proportions whether it is 1280 by 720 or 1920 by 1080. Keeping the ratio fixed when you resize is what stops an image or video from looking stretched.
How do I work out the missing width or height?
Multiply or divide by the ratio. For a ratio of w to h, the height is width times h divided by w, and the width is height times w divided by h. So at 16:9 a width of 1280 gives a height of 1280 times 9 / 16 = 720. This tool does that calculation automatically as you type into either field.
What are the common aspect ratios?
16:9 is the standard for modern video and most screens, 4:3 is the older television and monitor shape, 1:1 is a square (common for social avatars and posts), 3:2 is typical of photography, and 21:9 is ultrawide cinema. The preset buttons set these instantly, and you can always type a custom ratio of your own.
Is anything sent to a server?
No. The calculation is simple arithmetic that runs entirely in your browser. Nothing you type is uploaded, logged, or stored, and the tool works offline once the page has loaded.