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Aspect ratio calculators

Calculate an aspect ratio from any width and height, or solve a missing side from a locked shape, with Instagram, YouTube and TikTok pages for their shapes.

Which aspect ratio page do you need

All four run the same arithmetic. What differs is the set of shapes offered beside it, and on a platform page those are that platform's own published shapes rather than a general list.

  • Aspect ratio calculator: start here when the shape is the question rather than the platform. Any two of width, height and ratio give the third.
  • Instagram aspect ratio calculator: four shapes, and a feed that crops anything outside them from the centre without telling you which part it took.
  • YouTube aspect ratio calculator: one shape for the player, the thumbnail and the banner, and a second, separate one for Shorts.
  • TikTok aspect ratio calculator: vertical by default, with a shorter shape for photo posts and an interface drawn on top of whatever you upload.

How an aspect ratio is worked out

The maths is one division and one reduction, and the interesting part is what happens when the reduction produces something unreadable. These pages handle that the same way everywhere.

  • Divide both sides by their greatest common divisor. 1080 and 1350 share 270, so a portrait Instagram post is 4:5.
  • A shape is only printed as a ratio while both of its terms stay small. Beyond that it is shown as a decimal, because 540:283 is not something anybody pictures.
  • A known shape is recognised by proximity rather than by an exact match, which is what lets 1200x630 be called 1.91:1 when it divides to 1.9048.
  • The exact division is always shown as well, so nothing the page rounds is hidden from you.
  • Solving a side always rounds to a whole pixel, because a file cannot be 562.5 pixels tall.

The shapes worth committing to memory

Six shapes cover essentially everything published to a social platform. Learning them is quicker than looking up a pixel pair each time, because the pixel pairs change and the shapes do not.

  • 1:1: Square. Feed posts, avatars and carousel slides that have to share a shape.
  • 4:5: The tallest an Instagram feed post is allowed to be, which is why it takes the most screen.
  • 3:4: Taller than square, well short of full screen. TikTok photo posts and older camera stills.
  • 9:16: The whole phone screen. Stories, Reels, Shorts and TikTok video.
  • 16:9: Widescreen video and every YouTube thumbnail. The default shape of a television and a laptop.
  • 1.91:1: The link card and landscape feed shape. It comes from the golden ratio, not from round numbers.

When the shape is not what is wrong

Plenty of posts that look wrong are the right shape already. It is worth ruling the other causes out before re-exporting anything, because a second export costs quality and fixes nothing.

  • If the picture looks soft rather than cropped, the problem is resolution or compression. A shape has no resolution of its own.
  • If the subject is cut off but the shape is correct, the crop was taken from the centre and the composition needs moving, not the numbers.
  • If text is unreadable, check it at the size it is displayed. Feed posts, thumbnails and grid tiles are all seen far smaller than they are made.
  • If bands appear around a video, the upload is the wrong shape for that player and no cover or thumbnail change removes them.
  • If you need the file itself rather than the number, use the image resizer, which exports to these shapes in your browser with nothing uploaded.
The rest of the job

You just fixed one post. Now do the month.

The aspect ratio calculators solves one piece of one post. OctoSpark plans, writes and schedules the whole calendar across every network you use, publishes it for you, and reports what actually performed.

  • One calendar for every network
  • Schedule once, publish everywhere
  • Drafts written in your own voice
  • See what actually performed
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No card needed. These tools stay free either way.

Frequently asked questions

How this tool works, what it cannot do, and what happens to what you put into it.

  • What is an aspect ratio?

    The relationship between a picture's width and its height, written as two numbers. It survives resizing: shrink a 16:9 frame and it is still 16:9, which is why platforms enforce shapes rather than pixel counts.

  • What is the most common aspect ratio on social media?

    It depends on the surface rather than the platform. Vertical 9:16 covers stories, Reels, Shorts and TikTok; 4:5 is the tallest feed post Instagram allows; 16:9 carries YouTube video and thumbnails; 1:1 carries avatars and carousels.

  • How do I change a photo to a different aspect ratio?

    Crop it or pad it. Cropping keeps the pixels and loses the parts outside the new shape, usually taken from the centre. Padding keeps the whole picture and adds bands. Our image resizer does both, in your browser.

  • Do these calculators upload my images?

    There is nothing to upload. These pages work on numbers rather than files: you type a width and a height, and the arithmetic runs in your browser. No file is ever chosen, sent or stored.

  • Is my data private?

    Yes. This tool does its work in your browser, so whatever you type, paste or upload stays on your device. Nothing is sent to our servers, which is also why it keeps working if you go offline after the page has loaded.

  • Is this really free?

    Yes. Every tool here is free with no account, no credit card and no usage cap. They exist so that the people who need our scheduling product find us, which only works if the tools are genuinely useful on their own.

  • Do I need an account?

    No. Open the page and use it. An account is only for OctoSpark itself, where you plan, schedule and publish a whole calendar rather than fixing one post at a time.

  • Can I use the output commercially?

    Yes. Anything you produce here is yours, including for client and commercial work. We claim no rights over it and we do not watermark it.