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ToolWrenResize images or video without distortion. Enter the original width and height, then type a new width or height and the other value is calculated to preserve the ratio.
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Aspect Ratio is a free, private online tool that lets you keep an aspect ratio when resizing: enter the original size and one new dimension to get the other. It runs entirely in your browser, so nothing you enter is uploaded to a server.
Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.
An aspect ratio expresses the proportional relationship between width and height, like 16:9 or 4:3. Keeping it constant when resizing prevents stretching or squashing.
Given the original dimensions and one new side, the other is found by simple proportion: newH = newW × origH ÷ origW. The tool also shows the simplified ratio using the greatest common divisor.
16:9 (widescreen video), 4:3 (classic displays), 1:1 (square social posts), 9:16 (vertical/stories) and 3:2 (photography) are the ones you'll meet most often.
An aspect ratio is the proportional relationship between an object's width and height, written as two numbers like 16:9 or 4:3. It describes shape independent of size: a 1920×1080 image and a 1280×720 image are both 16:9. Keeping the ratio constant when resizing is what stops images and video from looking stretched or squashed.
To resize without distortion, the new dimensions must keep the same ratio. If you know the original width and height and one new dimension, the other follows by simple proportion: new height = new width × original height ÷ original width. This tool does that calculation for you and also reduces the ratio to its simplest whole-number form using the greatest common divisor.
A few ratios dominate: 16:9 for modern video, TVs and monitors; 4:3 for older displays and some photos; 1:1 square for social posts and profile pictures; 9:16 vertical for phone 'stories' and short-form video; and 3:2 for much of photography. Matching the right ratio to the platform avoids awkward cropping.
If you change width and height independently, the content distorts — faces stretch, logos skew. If you crop to a new ratio carelessly, you can chop off important parts of the image. Calculating the correct matching dimension first lets you scale cleanly, and knowing the simplified ratio tells you instantly whether content will fit a target frame.
Resize images and video for specific platforms, work out letterboxing or pillarboxing, set up canvas and export sizes in design tools, and check whether footage shot in one ratio will fit another. Everything is calculated in your browser.