Aspect ratio calculator

Enter a width and height to find the aspect ratio, or pick a ratio and type one side to get the other.

Find the aspect ratio

16:9

Widescreen, YouTube, TV · 1.778

Resize and keep the ratio

Ratio

Type either side and the other is filled in.

Runs on your device. Images you read sizes from are never uploaded.

How it works

  1. The width and height are divided by their greatest common divisor to give the simplest exact ratio.
  2. If that ratio is close to a common one, such as 16:9, it is named for you.
  3. To resize, the other side is calculated from the ratio and rounded to whole pixels.

Supported formats

Opens
Any image, if you want to read its size. The calculator works without one.
Saves
Nothing to download. The results are numbers.

Your image stays on your device

This tool runs entirely in your browser. The image is never uploaded, so there is nothing for us to store, see or delete.

To check, open your browser’s developer tools, switch to the Network tab and use the tool: you will not see your image being sent anywhere.

Questions

What is an aspect ratio?

The shape of an image, written as width to height. 16:9 is widescreen, 4:3 is a classic photo, 1:1 is square. Images with the same ratio can be resized into each other without stretching or cropping.

Why does 1366 × 768 not come out as exactly 16:9?

Because 1366 is not quite 16/9 of 768. The exact ratio is 683:384, which is very close to 16:9, so the calculator shows both.

Which ratio should I use for social media?

1:1 or 4:5 for Instagram posts, 9:16 for stories, Reels and TikTok, and 16:9 for YouTube videos and thumbnails.