Video Aspect Ratios: 16:9, 9:16, 1:1 and 4:5 Sizes
By Mark Fulton · 2026-09-07 · 13 min read
An aspect ratio is the shape of the frame, written as width to height, and nothing else. 16:9 is landscape, 9:16 is the same shape stood on end, 1:1 is square, 4:5 is the slightly tall rectangle the Instagram feed favours. A ratio is not a resolution: 1280x720 and 3840x2160 are both 16:9, and picking a ratio tells you the shape while picking a resolution tells you how many pixels are used to draw it. The rule that removes most of the confusion is that the number people quote, the 720 or the 1080, names the short edge of the frame. So 16:9 at 1080 is 1920x1080 and 9:16 at 1080 is 1080x1920. And here is the part the spec cards leave out: you cannot change a ratio for free. Reshaping a frame either throws picture away or gives up screen area, and which one you should accept depends entirely on where your subject sits in the frame.
That is the whole vocabulary. The rest of this page turns it into numbers you can copy, then works through the trade you are actually making when a landscape clip has to go somewhere vertical.
What does an aspect ratio actually describe?
Three separate things get collapsed into one word, and untangling them fixes most of the guesswork.
Ratio is proportion. It has no units. A 16:9 frame is 16 units wide for every 9 units tall, which is a decimal 1.778 if you divide it out. Cinema ratios are usually written as a decimal for exactly that reason: 1.85:1 and 2.39:1 are ratios stated with the height normalised to 1.
Resolution is the pixel count. 1920x1080 is a resolution. It happens to be 16:9 because 1920 divided by 1080 is 1.778, but the ratio is a consequence of the two numbers, not a fourth piece of information.
Orientation is which way up the rectangle is. Landscape means wider than tall, portrait means taller than wide. 16:9 and 9:16 are the same proportion in the two orientations, which is why converting between them is a rotation of the target shape rather than a change in how much rectangle you have.
There is a fourth term that surfaces when a file behaves strangely. Pixel aspect ratio is whether the pixels themselves are square. Modern digital video uses square pixels, so storage resolution and display shape agree. Older broadcast formats did not, which is why an anamorphic file can report 720x480 and still play at a widescreen shape. FFmpeg's scale filter documentation describes this directly: the filter "forces the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio." If a file's stated dimensions and its on-screen shape disagree, that flag is usually why.
Then there is the naming convention that trips people up daily. "1080p" originally meant 1080 horizontal lines, which is height. That works cleanly for landscape. It breaks the moment the frame is vertical, because a vertical clip that people call 1080p is 1080 pixels wide and 1920 tall. The consistent way to read it, and the way the table below is built, is that the label names the short edge.
Which ratio does each platform want?
Here is the conversion table. The pixel dimensions are arithmetic from the ratio, not a claim about any platform, and every one is even on both axes because H.264 with 4:2:0 chroma requires it.
| Ratio | 4K tier | 1080 tier | 720 tier | Where it is used | What a mismatch looks like after upload |
|---|---|---|---|---|---|
| 16:9 | 3840x2160 | 1920x1080 | 1280x720 | Landscape video everywhere: YouTube on a computer, most embedded players, presentations, TVs | Fine on a landscape player. Dropped into a full-screen vertical feed it becomes a thin band across the middle with a large empty area above and below |
| 9:16 | 2160x3840 | 1080x1920 | 720x1280 | Full-screen vertical: Reels, TikTok, Shorts, Stories | On a desktop landscape player it gets padded on both sides. YouTube's own help page describes that padding as white by default and dark gray in dark theme |
| 1:1 | 2160x2160 | 1080x1080 | 720x720 | Square feed posts, profile and ad placements, thumbnails | Bars on the sides in a landscape player, bars top and bottom in a full-screen vertical feed. It is the ratio that never quite fills anything |
| 4:5 | 2160x2700 | 1080x1350 | 720x900 | The tall Instagram feed post: more screen than a square without going full height | Side padding on any landscape player. Slightly letterboxed in a full-screen vertical feed |
| 4:3 | 2880x2160 | 1440x1080 | 960x720 | Older footage, some screen recordings, document cameras | Thin pillars on both sides of a 16:9 player. Rarely a problem, rarely ideal |
A few notes on reading it.
The 4K tier holds the short edge at 2160, which is what makes the numbers comparable across rows. That means the vertical 4K row is 2160x3840, a very large frame, and the 4:5 row is 2160x2700. Nobody calls those "4K" in conversation, but the arithmetic is the arithmetic.
The 21:9 ultrawide row is missing on purpose. True 21:9 at 2160 tall works out to 5040x2160, while the panels sold as 21:9 are 2560x1080 and 3440x1440, which are 2.370 and 2.389 rather than 2.333. Publishing a clean number for that row would mean publishing a wrong one.
On platform specs, the only figures worth trusting are the ones a platform publishes itself, and they move. As of 7 September 2026, YouTube's own video resolution and aspect ratios page states that "the standard aspect ratio for YouTube on a computer is 16:9" and lists the 16:9 resolution ladder as 7680x4320, 3840x2160, 2560x1440, 1920x1080, 1280x720, 854x480, 640x360 and 426x240. The same page advises against baking bars into your file yourself, because the player adapts to your real dimensions and manual padding fights that. YouTube's Shorts help page, read the same day, says Shorts can be "up to 3 minutes long" and that "you can upload Short videos with a maximum resolution of 1080p."
For Instagram the useful thing to know is that it publishes a permitted range rather than a single recommended size. The exact figures, quoted off Instagram's own reel size help page on 31 August 2026, are in our Instagram Reels sizing guide, along with the arithmetic for what a landscape source actually produces. Anywhere else, check the platform's own help page on the day you need the number. Third-party spec cards go stale quietly.
Crop, pad or reframe: what does each cost?
This is the section the spec pages skip, and it is the only part that requires a decision.
A 16:9 frame cannot become a 9:16 frame with everything intact at full size. The shapes are incompatible. You have three ways out and each one bills you differently.
Crop bills you in picture. Keep the full height, discard the sides. The largest 9:16 rectangle that fits inside 1920x1080 is 608x1080, because 1080 times 9/16 is 607.5 and encoders need an even number. You keep every pixel you keep at full quality, but you have thrown away 68 percent of the width. Whatever was near the left or right edge is gone, and no amount of processing brings it back.
The arithmetic improves sharply with a bigger source. A 3840x2160 clip cropped to 9:16 lands at roughly 1214x2160, which is still comfortably above 1080 wide after the crop. That is the strongest practical argument for shooting landscape at 4K when you know a vertical cut is coming. The crop then costs you framing, not resolution.
Pad bills you in screen area. Keep the whole frame, add bars around it. Fit 1920x1080 inside a 1080x1920 canvas and the picture band is 1080x608, floating in the middle. Nothing is lost from the image, but the picture occupies under a third of the height. On a feed where everything else runs edge to edge, that reads as a repost rather than a native post. It is also the version that puts your bars in front of the viewer for two thirds of the screen, which is why people fill them with blurred copies of the video or with captions.
Reframe bills you in attention or money. This is crop with a moving crop window that follows the subject rather than sitting fixed in the centre. Doing it by hand in an editor is the highest quality option and takes real time. Automated subject tracking is what a lot of paid tools sell, and it works well on a single centred speaker and much less well on anything with two subjects, fast motion, or a subject that leaves frame.
The decision rule is simpler than the options suggest. If the subject sits near the centre of your landscape frame, crop and stop thinking about it. If the important content is spread across the full width, a two-shot, a wide landscape, a slide with text running edge to edge, then cropping destroys the thing you are trying to show and padding is the honest choice. If the subject moves across the frame, that is the one case where a manual reframe earns its time.
One thing worth saying plainly: VidClip has a crop tool and it does not have a pad tool. If you decide padding is the right call for a particular clip, you will need an editor for it. The centre crop is on the site and runs instantly.
Why do black bars appear after uploading?
Because a player was handed a frame whose shape did not match its container, and the safest thing a player can do with a mismatch is fit the whole picture inside and fill the leftover space.
MDN's documentation for CSS object-fit names the three possible behaviours precisely, and every video player is choosing between them. With contain, "the entire object is made to fill the box, while preserving its aspect ratio, so the object will be letterboxed or pillarboxed if its aspect ratio does not match the aspect ratio of the box." With cover, "if the object's aspect ratio does not match the aspect ratio of its box, then the object will be clipped to fit." With fill, the content "will be stretched to fit."
Those are your three failure modes, and they are worth learning to recognise on sight:
- Letterboxing is bars above and below. It happens when your video is wider than the space it landed in. A 16:9 clip in a square post letterboxes.
- Pillarboxing is bars on the left and right. It happens when your video is taller than the space. A 9:16 clip on a desktop player pillarboxes, which is exactly the padding YouTube's help page describes.
- Stretching is nobody's default and looks obviously wrong: faces go wide or narrow. If you are seeing it, something in the chain has a bad pixel aspect ratio flag rather than a shape mismatch.
A fourth case looks like a bug but is not. Some platforms crop rather than pad, so instead of bars you get a frame with the top and bottom of the picture missing. Nothing broke. The player chose cover behaviour and clipped.
There is one case where the bars are baked into your file and no player can help. If your source already has black bars burned into the pixels, from an old export or a screen recording of a padded player, then those bars are picture as far as any tool is concerned. Crop them off first, then treat the result as your real frame.
How do you change a ratio without an editor?
Two steps, in this order, and it matters which order.
Step one, set the shape. Ratio is a crop operation, so it belongs to the crop tool. Pick 9:16, 4:5, 1:1 or 16:9 and it takes the largest rectangle of that shape that fits inside your source, centred on both axes, rounded to even dimensions on both edges so the encoder accepts it. FFmpeg's crop filter documentation describes the same operation: it crops "the input video to given dimensions" from an origin you specify. Centre is the right guess for most footage because subjects tend to sit near the middle, and it is the guess the tool makes for you.
Step two, set the size. Once the shape is right, the resize tool sets how many pixels draw it. One thing to know before you use it: the resizer targets height, with presets at 480, 720 and 1080, and it only downscales. On a landscape clip, choosing 1080 gives you 1920x1080. On a vertical clip, choosing 1080 gives you 1080 tall and 608 wide, not 1080x1920, because the height is what you are setting. If you want a 1080x1920 export you are asking for 1920 of height, which is above the presets, so the answer there is to crop to 9:16 and leave the result at its native size rather than resizing it down.
Skip step two entirely if the crop already left you at a sensible pixel count. Cropping a 4K clip to 9:16 gives you roughly 1214x2160, which is more than enough for any feed, and resizing it further only throws away detail.
Both steps run on your own machine. VidClip loads FFmpeg compiled to WebAssembly into the page, reads the file from your disk into browser memory, and does the work on your CPU. There is no upload, no queue and no account. The free tier caps input files at 200 MB and puts a small semi transparent mark in the corner of video exports. Pro removes both.
Frequently asked questions
What is 9:16 in pixels?
There is no single answer, because 9:16 is a shape and pixels are a quantity. The three sizes people mean in practice are 1080x1920, 720x1280 and 2160x3840, in decreasing order of how often they get quoted. 1080x1920 is the working default for vertical social video and is what someone means when they say "1080p vertical", even though it is 1080 wide rather than 1080 tall. Any pair where width divided by height equals 0.5625 is 9:16, so 540x960 and 360x640 qualify too, they are just smaller.
Is 4:5 better than 1:1 for feed posts?
For a scrolling feed, 4:5 takes up more vertical space on a phone screen than a square does, and screen space is roughly what attention costs. That is the entire argument in its favour and it is a real one. The counter argument is that 1:1 behaves identically in every orientation and never needs a second version, which matters if the same asset has to run in several placements. If you are producing one video for one feed, 4:5 is the better use of the screen. If you are producing one asset to reuse across placements, square saves you the exports.
How do I turn a landscape video vertical?
Crop it, and accept that you will lose the sides. Take the 16:9 clip into the crop tool, pick 9:16, and the largest vertical rectangle that fits gets taken from the centre. From a 1920x1080 source that is 608x1080. From a 3840x2160 source it is about 1214x2160, which is why a 4K original survives the operation far better. Before you crop, look at where your subject actually sits: if the person or the product is roughly centred, a centre crop is all you need. If the content runs across the full width, cropping is the wrong tool and you want padding in an editor instead, because the alternative is deleting the point of the shot.
Why does my video have bars on the sides?
That is pillarboxing, and it means your video is taller in proportion than the space it was placed in. A 9:16 or 4:5 clip on a landscape player is the usual cause, and the player is preserving your whole frame rather than clipping it. It is not a fault in your file. If you want it to fill that landscape space instead, the fix is to crop the video to the player's shape, which means giving up the top and bottom of your picture. If the bars are in the file itself rather than added by the player, drag the timeline handle and check: bars added by a player disappear when you open the file locally, bars burned into the pixels do not.
Got a landscape clip that needs to go vertical? Set the ratio in the crop tool first, then set the height in the resizer if the result is bigger than it needs to be. Both run in the browser on your own machine, so the file never leaves your disk and there is nothing to wait in line for.