Aspect Ratio Calculator

Find missing width or height — choose preset or enter custom ratio

Aspect Ratio

:

Simplified: 16:9

Enter Width → Get Height

Calculate dimensions for any aspect ratio

1080.00

Calculated Dimensions

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About the Aspect Ratio Calculator

This aspect ratio calculator finds the missing dimension for a given ratio: type a width and get the matching height. It covers 16:9, 4:3, 21:9, 1:1 and custom ratios, so images and video scale without stretching.

An aspect ratio calculator answers the question that comes up whenever something is resized: if the width has to be 1280, what height keeps the proportions? Guessing produces stretched faces and letterboxed video, and doing the division by hand for every asset is tedious.

Common presets are built in — 16:9 for video and most screens, 4:3 for older displays and many camera sensors, 1:1 for social avatars and product grids, 21:9 for ultrawide — and any custom ratio can be entered.

It also works in reverse: give it an existing width and height and it reduces them to the simplest ratio, which is how you find out whether an asset is 16:9 or something slightly off that will be cropped on upload.

How to use the Aspect Ratio Calculator

  1. Choose a ratio. Pick a preset such as 16:9, or enter a custom ratio.
  2. Enter one dimension. Type either the width or the height you need.
  3. Read the other dimension. The matching value is calculated to keep the ratio exact.
  4. Or find an existing ratio. Enter both dimensions to reduce them to their simplest ratio.

Aspect Ratio Calculator features

  • Presets for 16:9, 4:3, 1:1, 21:9, 9:16, 3:2 and 2.39:1
  • Enter one dimension and get the other
  • Custom ratios as well as the presets
  • Ratio reduced to its simplest form
  • Copy the result
  • Runs in your browser; nothing is uploaded

Frequently asked questions

What does this actually calculate?

The missing dimension. Give it a ratio and one measurement and it returns the other, so an image or video scales to fit a space without being stretched or letterboxed.

Which ratio should I use?

16:9 for video and most screens, 1:1 for square social posts, 9:16 for vertical video and stories, 4:3 for older displays and many camera sensors, 21:9 for ultrawide monitors, and 2.39:1 for cinematic widescreen.

Why does stretching an image look so wrong?

Because changing the ratio distorts every shape in the frame, and faces and circles are the ones people notice immediately. Keeping the ratio and cropping the excess almost always looks better than distorting to fit.

How does this help with responsive layouts?

It gives you the padding or height that reserves the right space for a media box at a given width, which is what prevents the page shifting as an image loads — the layout-shift problem Core Web Vitals measures.

Can I use a ratio that is not in the list?

Yes, enter both sides of the custom ratio. It is reduced to its simplest form, so entering 1920:1080 is the same as entering 16:9.