Instagram post size, and the sizes for every other network

The size almost everybody arrives looking for

The question is nearly always asked in pixels ("what size is an Instagram post?") and the networks do not answer it in pixels. They answer it in ratios. Instagram does not check whether your image is 1080 wide, it checks whether width divided by height lands inside the band that format accepts. Which is why an answer in pixels goes stale every time a platform changes screen density, and an answer in ratios never does.

Translated back into pixels, the Instagram feed band gives three useful sizes off the same starting width. At 1080 wide, 4:5 is 1080×1350, the square is 1080×1080, and the landscape edge at 1.91:1 is 1080×566. All three publish. The 1080×1350 one takes up the most height on the phone of whoever is reading you, which is the only real advantage available in this decision, and the reason nearly every account that grows posts tall vertical even though the other two are accepted.

A 1080×1920 vertical, on the other hand, is 9:16 and falls outside that band. This is not an ugly crop: the Instagram feed and carousels refuse it. That is the single most common mistake here, and it comes from reusing a file made for a reel or a story somewhere the ratio is the rule. When a piece can be recycled and when it has to be exported again is in the content repurposing guide.

Ratios, pixels and weight, network by network

This table is the full list, by network and by format, of what an image is allowed to be. The required ratio column is the one that blocks; the recommended one is the shape that surface actually draws the piece at, which is a different thing and is almost always confused with it.

There are four readings worth taking from it before moving on. The first is that almost nobody imposes a hard ratio: only Instagram on feed and carousel, Pinterest, Snapchat, and LinkedIn through its pixel floor. Facebook, Threads, Reddit, Telegram, Discord and WhatsApp take whatever they are handed and draw it as best they can, so the decision there is aesthetic rather than technical.

The second is that two networks take no image at all in some of their formats, and it is worth knowing before the calendar is built. An Instagram reel and a Facebook reel are video uploads: a photo sent under one of them does not come out as a still, it is refused. YouTube goes further and takes no image in any format, neither as a video nor as a Short.

The third is the pixel floors, which are few and very specific. LinkedIn asks for 552×276, Snapchat for 540×960, Google Business for 400×300 and Pinterest for 100×100. Below those figures no crop helps, because nobody invents pixels that are not there. Above them there is room: the LinkedIn and Bluesky ceilings are warnings, not refusals.

The fourth is weight, and the number that surprises people is Bluesky. One megabyte per image is the lowest ceiling on the whole list by a factor of four, and a photo out of a modern phone clears it without trying. It does not block, but it is the network where you will compress before posting most often.

Video: ratio, length and weight

Video has its own bands and its own ceilings, and they do not match the image ones even inside the same network. A video in the Instagram feed has to land between 4:5 and 1.91:1 exactly like a photo, but it can run for sixty minutes; the same file as a reel may be vertical and is cut off at ninety seconds.

The case in that table that causes the most damage is Shorts. YouTube decides whether something is a Short or an ordinary video by looking at the ratio of the file, not at the box you ticked when you uploaded it, so a 16:9 sent as a Short publishes as a long video and says nothing. It is one of the very few ratio rules that is checked before publishing and blocked, and it is blocked precisely because the warning would arrive when nothing can be done about it. The way out is not to crop the file, it is to change the format.

The second case is LinkedIn, which has the widest video band of the lot: from 1:2.4 all the way to 2.4:1. Almost anything fits, including a panorama no other network would take. What does not fit is the extreme vertical that gets exported for TikTok with bars, and that is the only video LinkedIn refuses on shape.

The third is the minimum length. Instagram, LinkedIn and TikTok want three seconds, Snapchat five and Pinterest four. It sounds like an irrelevant detail until somebody tries to publish a two second loop cut from a product shoot, which is a real piece of work that none of those four networks accepts as it is. What makes a short video work once it does get in is in the reel retention guide.

What blocks a post and what only makes it look bad

Here is the distinction most size cheat sheets never make, and the genuinely useful part of this page. Not every rule above weighs the same. Some are facts about the file that nothing along the way can fix, and others are things a delivery pipeline does every day without asking.

The line is drawn between geometry and encoding, and it is drawn there on purpose. Recompressing an image, scaling it down or trimming a video are ordinary operations: if a piece is heavier than the ceiling, the likely outcome is that it goes out anyway, slightly worse. Changing the ratio of a photo, on the other hand, means deciding which part of the image gets thrown away, and nobody does that for you in silence. Nor is there any way to lift a photo above a network's pixel floor: the missing pixels cannot be invented.

That gives a practical rule for working. The three things to get right before exporting are the ratio, the pixel minimum and the kind of file the format takes, because those are the three that stop a post. Weight, length and the resolution ceiling are warnings: worth reading, worth respecting if you care about quality, and none of the three will leave a piece unpublished on a Tuesday at nine. Working this way also avoids the opposite mistake, which is blocking out of caution something that would have gone out fine.

How much text fits, and the two fields nobody fills in

Image sizes are half the problem. The other half is the caption, and the limits there are far more uneven than people assume.

When the same piece goes to several networks at once, the shortest limit in the group is the one in charge. A caption written for Instagram's 2,200 characters does not fit into Bluesky's 300 or Snapchat's 250, and trimming it at the end is five times the work of writing it for the narrowest network from the start. The same goes for file counts: a ten image carousel cannot be sent to YouTube, Pinterest or Snapchat, which take exactly one.

The two fields that get dropped first are alt text and the first comment. Alt text takes up to a thousand characters, five hundred on Pinterest, and only six of the fourteen networks in the table store it at all; the rest ignore it silently, which is no reason to stop writing it, because those six include the three that send the most traffic. The automatic first comment, where a lot of people park their hashtags or their link, is only automated on four networks; on the other ten a person pastes it by hand after publishing, which is sustainable at three pieces a week and stops being sustainable at fifteen.

One piece, several networks: choosing the crop

When one post goes out to several accounts at once there is one file, not one per network, and that file has to satisfy all of them simultaneously. That turns the crop into an intersection rather than a preference.

Most combinations have an answer. The Instagram feed, Facebook, LinkedIn and Threads all agree on the square and on 4:5, so a piece at 4:5 serves the four of them and happens to be the tallest of the accepted shapes on the first two. Adding TikTok or a story moves the answer to 9:16, and the Instagram feed drops out of the group at that point because of its band.

Some combinations have no answer, and saying so is more honest than offering a crop that will be refused anyway. The Instagram feed takes between 4:5 and 1.91:1; a YouTube Short takes portrait only. There is no single ratio that satisfies both, so those two accounts cannot share a file and the piece has to be published twice, from two exports. Scheduling the same idea on both without fighting the file is what the publishing calendar is for, and adapting a piece from one network to another automatically is covered on the cross posting page.

The working summary fits in three sentences. Export at 4:5 if the piece is going to feeds and at 9:16 if it is going to vertical formats, and do not try to make one file serve both. Check the ratio, the pixel floor and the file kind before exporting, because those are the only things that block. And write the caption for the narrowest network in the group, because trimming text at five to nine is how captions that say nothing get published.