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Shape first, pixels second

16:9 is not a size. It is a shape

The ratio decides what survives the crop; the resolution decides how sharp it looks. Pick the shape, type one side, and read the other side - plus the same shape at every common resolution, rounded to numbers an encoder accepts.

Short answerLast edited October 31, 2026

The Aspect Ratio Calculator finds the missing width or height of a frame in a ratio such as 16:9, 9:16 or 1:1, and identifies the ratio of a size you already have. For 1920 pixels wide at 16:9, the height is 1080 pixels.

Why the same video looks different on two apps

Aspect ratio is width divided by height, and it says nothing about how many pixels there are. 1920 by 1080 and 3840 by 2160 are both 16:9: identical shape, four times the detail. 1080 by 1080 is square, and 1080 by 1350 is 4:5 - the same width, a taller frame, and a completely different crop of the same recording.

What a platform does with the wrong shape is the part that costs time. A vertical app given a horizontal video either adds blurred bars above and below or crops the sides; a horizontal player given a vertical video fills the screen with black. Neither is a resolution problem, and no amount of extra pixels fixes it.

That is why the ratio is decided before the shoot, not after. If the same interview has to exist as a 16:9 YouTube upload and a 9:16 Short, it is framed once with room on the sides, so the vertical cut keeps the face instead of the wallpaper behind it.

The six shapes you will actually need

16:9 - landscape

YouTube, television, a laptop screen, a webinar. The default everything was built around, and the shape that loses the most when it is cropped to vertical.

9:16 - vertical

Reels, Shorts, TikTok, Stories. Full screen on a phone held upright, which is why the subject has to be centred in the middle third of a horizontal frame.

4:5 - feed portrait

Instagram and Facebook feed posts. Taller than square, shorter than a story: the largest shape those apps show without cropping in the feed.

1:1 - square

Profile grids, product shots, carousels that have to line up. Forgiving on any screen and easy to assemble from a wide original.

4:3 - classic

Older footage, iPad screen recordings, some presentation exports. Slightly taller than 16:9, so it crops a widescreen frame least.

2.39:1 - anamorphic

Cinema trailers and film-style edits. Wide enough to demand letterboxing on a 16:9 player, which is the intended look rather than a mistake.

What each ratio costs when you crop a 16:9 original

The decimal is the ratio the encoder actually sees; the crop column is what you lose from a landscape master
RatioDecimalUsed byCropping a 16:9 master
16:91.778YouTube, TV, webnothing - it is the source
4:31.333iPad, archive footagesides trimmed, mild
1:11.000grids, product shotssides trimmed, noticeable
4:50.800Instagram feedsides trimmed, heavy
9:160.563Reels, Shorts, TikTokonly the middle survives
21:92.333ultrawide, trailersbars added, nothing lost
2.39:12.390cinema lookbars added, nothing lost

Pick, type, read

1

Choose the shape

A preset, or a custom pair such as 7:3 for a banner. The frame above the numbers shows the shape immediately.

2

Type one side

Enter the width you have and the height follows - or the height, and the width follows. Both stay even numbers.

3

Use the scale list

The same shape at 480p, 720p, 1080p, 1440p and 2160p, rounded for encoders, so one decision covers every export.

Questions about ratios and crops

Why are the results rounded to even numbers?
Because video codecs work in blocks of pixels and most encoders refuse odd dimensions for the chroma channels. A 1081-pixel height is not something you can export reliably; 1080 is. The tool rounds to the nearest even number, which is at most one pixel away from the exact ratio.
Is 4:5 the same as 1080 by 1350?
It is the same shape at that size. 1080 by 1350 is a 4:5 frame, and 1080 by 1350 is the usual Instagram recommendation. The ratio is the shape; the numbers are one instance of it.
How do I get a 9:16 video out of a 16:9 recording?
Either crop the middle - which keeps the full height but throws away the sides - or place the landscape frame in a vertical canvas with blurred copies of itself above and below, which keeps everything and fills the screen. The second is what most Reels do; the vertical video converter does it automatically.
What does 2.39:1 mean in pixels?
For a 1920-pixel width it is about 803 pixels high, usually rounded to 800 or 804. The exact cinema ratio varies between 2.35 and 2.39 depending on the era, which is why the decimal matters more than the label.
Does changing the ratio change the file size?
Yes, through the pixel count. Cropping 16:9 to 9:16 at the same width keeps fewer pixels, so the file gets smaller at the same bitrate; padding to a vertical canvas adds pixels and makes it bigger. The bitrate budget is what decides the quality either way.
Can I use this for images and print?
The arithmetic is identical: width divided by height, scaled to whatever long edge you need. For print, replace pixels with millimetres in the same fields and the shape stays correct - 4:5 at 200 mm wide is 250 mm high.

Decide the shape once

Type one side, read the other, and export the same shape at every size you need.

Calculate my ratio

Quick facts

  1. 16:9 at 1920 pixels wide is 1080 tall, and the same ratio at 1080 wide is 607.5, which is rounded to 608.
  2. A 1080-pixel square is 56% of the 1920-pixel width of a 16:9 frame, which is why a square crop loses the sides of a wide video.
  3. A 9:16 frame is 1080 × 1920 pixels at the size TikTok, Reels and Shorts display, while 16:9 is 1920 × 1080.WHATWG
  4. App buttons, captions and profile names sit over the bottom and right edge of a vertical video, so text belongs in the middle of the frame.WHATWG
  5. H.264 is the codec that made HD video practical on the web: it is decoded by every current browser and phone without a plugin.ITU-T

Questions people ask

What is the aspect ratio of a vertical video?
Vertical video for phones is usually 9:16, which is 1080 by 1920 pixels. The same 16:9 frame turned on its side gives a portrait frame of 9:16 at the same height, which is why it fills a phone screen.
How do I find the ratio of an image?
Divide the width by the height and reduce the fraction. 1920 × 1080 gives 1.777…, which is 16:9. Divide both numbers by their greatest common divisor, here 120, to get 16 and 9.
What aspect ratio should I use for Instagram or YouTube?
YouTube’s standard video is 16:9, and Shorts are 9:16. Instagram feed posts accept 4:5 portrait, square and landscape formats, while Reels and Stories use 9:16. Check each platform’s help page, since the accepted ratios change over time.

What this page is about

  • Vertical video

    Video framed at 9:16 for phones, where the interface of the app covers the edges of the picture.

  • H.264 / AVC

    The video codec standardised by ITU-T as H.264 and by ISO/IEC as MPEG-4 AVC, decodeable by every current browser.

Official sources cited on this page

  1. HTML Living Standard (canvas, file input, media elements)WHATWG
  2. Recommendation H.264: Advanced video coding for generic audiovisual servicesITU-T

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