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Aspect ratio calculator

Find a missing width or height for any aspect ratio, or the ratio of any frame size.

  • Free, no account
  • Runs in your browser, nothing uploaded

Runs in your browser. Nothing is uploaded.

Result

Change any number and the answer updates.

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00:20How it works

How to work out an aspect ratio

  1. Choose what you wantFind the missing side for a ratio, find the ratio of a frame size, or resize a frame and keep its shape.
  2. Type the numbers you knowThe answer updates as you type.
  3. Read the answerRounded to even numbers, with the exact value and the working shown.
00:30The details

What goes in and what comes out

Privacy
The sums run inside your browser. Nothing you type is sent anywhere.
Cost
Free. No account, no watermark, no trial that runs out.
00:35Worth knowing

Getting a good result

What an aspect ratio is

The shape of a frame: its width compared with its height. 16:9 is 16 units wide for every 9 high, whether that is 1280 × 720 or 3840 × 2160. To find a height from a width, multiply by the second number and divide by the first.

The ratios video uses

16:9 for YouTube, televisions and most screens. 9:16 for Reels, Shorts, TikTok and Stories. 1:1 for square posts. 4:5 for portrait posts in a feed. 4:3 for older video and many webcams. 21:9 for wide cinema.

Why the answer is rounded to even numbers

H.264 and most other video encoders need a width and a height that divide by two. A frame of 1366 × 768.375 has to become 1366 × 768 before it can be encoded.

00:40Questions

Aspect ratio calculator: common questions

What ratio is 1920 × 1080?

16:9. Both numbers divide by 120.

What is 1080 wide at 9:16?

1080 × 1920.

Is 1366 × 768 really 16:9?

Not exactly: it reduces to 683:384, which is very close. The calculator says when a size is a near miss.

Is anything I type sent anywhere?

No. The sum is done by your browser.

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