Aspect Ratio Calculator — Free Online Tool
Calculate correct width or height for any ratio
How to use this tool
- [01]Enter the aspect ratio you need, or two dimensions to derive it.
- [02]Enter the width or height you know, and read the matching value.
- [03]Resize to both figures together — changing one without the other is what stretches an image.
About this Aspect Ratio Calculator
The Aspect Ratio Calculator solves for the missing dimension when you know a ratio and one side, so resizing keeps proportions intact instead of stretching the content.
Stretching is the failure it prevents, and it is immediately visible to a viewer even when they cannot name what is wrong — faces widen, circles become ovals, and type distorts. Any resize that changes width and height by different factors does this, which is why the calculator exists as a step before resizing rather than as a fix afterwards.
The ratios that come up repeatedly are worth recognising: 16:9 for video and most screens, 4:3 for older displays and many camera sensors, 1:1 for square social posts, 4:5 for the tallest image Instagram allows in a feed, 9:16 for vertical stories and short-form video, and 2:1 or thereabouts for web banners. Knowing that 1920x1080 and 1280x720 are the same shape, while 1920x1200 is not, resolves a lot of confusion about why an export looks different from the preview.
It is also useful in the other direction — deriving the ratio from dimensions you already have, which is how you find out that a source video is 2.39:1 cinematic rather than 16:9 and will letterbox on a standard player.
Calculation is instant in your browser.
Our Aspect Ratio Calculator is completely free to use with no signup required. For this tool, processing runs in your browser — your files and data stay on your device and are not uploaded to our servers.
Whether you are a developer, designer, student, or business owner, this tool is designed to save you time and make your workflow more efficient. Bookmark this page to access it whenever you need it — it will always be free.
Frequently asked questions
Is the Aspect Ratio Calculator completely free?
Yes, the Aspect Ratio Calculator is 100% free to use with no hidden charges, no subscription, and no signup required. Simply visit the page and start using it immediately.
Does this tool upload my files to a server?
No. Everything runs entirely in your browser using JavaScript. Your files, text, and data never leave your device and are never sent to our servers. This makes it completely private and secure.
Does the Aspect Ratio Calculator work on mobile?
Yes, the Aspect Ratio Calculator is fully responsive and works on all devices including smartphones, tablets, and desktop computers. It works on Chrome, Firefox, Safari, and Edge browsers.
How accurate is this tool?
Our Aspect Ratio Calculator uses industry-standard algorithms to ensure accurate results every time. It has been tested extensively across different browsers and devices to ensure consistent and reliable output.
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