Instagram carousel sizes and specs that actually work

What size should an Instagram carousel be?

Use a width of 1080 pixels and pick one aspect ratio for the whole carousel. Instagram downscales anything wider than 1080 pixels, so exporting at 2160 or 4096 wide gains you nothing except upload time and a re-compression pass.

You will see 1080 × 608 quoted as "1.91:1 landscape" on a lot of sites. Do the arithmetic: 1080 ÷ 1.91 = 565.4, so 1.91:1 is 1080 × 566. 1080 × 608 is 16:9 wearing the wrong label.

Why does the first slide decide the size of every other slide?

Instagram crops the whole carousel to the aspect ratio of the first slide you add. Upload a 4:5 cover followed by square slides and those square slides get their sides cut off; upload a square cover followed by portrait slides and the portraits get cropped top and bottom.

The practical rule is simple: build every slide at the same pixel dimensions, and decide the shape before you design anything. Mixing ratios inside one carousel is the single most common way a deck that looked right in the design tool arrives on Instagram with headlines sliced in half.

Recent versions of the Instagram app offer a resize toggle at the preview step that can pad mismatched slides instead of cropping them, but the option is not documented by Meta and its behaviour varies by app version. Do not design around it.

What does the 3:4 profile grid crop off your cover slide?

Instagram’s profile grid has rendered posts at 3:4 since January 2025, and it centre-crops to get there — which means the grid always cuts the sides off, never the top and bottom. How much depends on the shape you posted.

A 4:5 portrait post (1080 × 1350) is shown at roughly 1012 × 1350 in the grid. It loses about 68 pixels of width, around 6% — roughly 34 pixels off each edge. Barely noticeable.

A 1:1 square post (1080 × 1080) is shown at 810 × 1080. It loses 270 pixels of width — a full 25%, or 135 pixels off each edge. That is a quarter of your cover slide gone in the grid view, and it is why square covers with text running edge to edge look fine in the feed and truncated on your profile.

The fix is a safe zone rather than a different ratio: keep cover headlines, logos and faces inside the middle ~74% of a square slide — about 13% clear on each side. Then the same cover reads correctly in the feed, in the grid, and in a Story reshare.

Several widely-shared guides claim vertical and square images are cropped "at the top and bottom" in the grid. That is geometrically impossible: going from a wider ratio to a narrower one removes width. Sides, always.

Should you use square or portrait for your carousel?

Portrait 4:5 occupies more vertical space in the feed, so it earns a longer look on the scroll — that is the case for it, and it is a real one. Square is easier to work with everywhere else.

Square slides survive being reposted to LinkedIn, X and Threads without recropping, they sit predictably next to each other in the grid, and charts and diagrams fit them more naturally than a tall rectangle. Portrait maximises one metric — feed height — at the cost of flexibility.

• Choose 4:5 portrait if Instagram is the only place this deck will ever appear and you want the largest possible feed footprint.
• Choose 1:1 square if the deck will be reposted elsewhere, contains charts or data, or you want a grid that stays visually consistent.
• Whichever you choose, apply it to every slide, and keep critical elements inside a side safe margin so the grid crop cannot reach them.
• Do not switch between shapes post to post if the profile grid matters to you — the mix reads as inconsistent even when each individual post is fine.

How many slides can an Instagram carousel have?

Twenty. Instagram’s Help Center states you can share up to 20 photos and videos in a single feed post, up from the previous limit of 10, which was raised during 2024.

Twenty is a ceiling, not a target. Completion rate falls with every additional slide, and a carousel nobody finishes is a carousel Instagram learns not to show. How many slides an Instagram carousel should have covers where the useful range actually sits and how to decide per post.

What file formats and file sizes does Instagram accept?

JPG and PNG for images; MP4 or MOV encoded as H.264 for video slides. A carousel can mix photos and videos freely — the Help Center wording covers "photos and videos" in a single post.

File size is where almost every specs guide goes wrong, so here is the honest position: Meta publishes hard file-size limits for Instagram advertising — 30 MB per image, minimum 500 pixels wide — and publishes essentially nothing for organic posts. The "8 MB maximum" and "60-second video slide" figures that appear on dozens of sites trace back to no primary source at all, and the quoted maximum video file size ranges from 250 MB to 4 GB depending on which blog you read.

In practice this never bites you. A 1080-pixel-wide PNG or high-quality JPG lands between 200 KB and 3 MB, comfortably under every limit anyone claims. Export at 1080 wide, use PNG for slides with text and flat colour, and stop worrying about the number.

If a specs page quotes a precise organic file-size limit without linking to a Meta page, treat it as folklore. Most of those numbers are Meta’s advertising specs with the word "ads" removed.

How long can the caption be, and how many hashtags are allowed?

Captions run to 2,200 characters and Instagram allows a maximum of 30 hashtags — the hashtag cap is one of the few numbers Meta documents directly, in its Instagram Feed ads guide.

The limit that actually shapes your writing is smaller. Instagram truncates the caption in the feed at roughly 125 characters behind a "…more" link, so the first sentence has to work on its own. Put the payoff or the question there; put context after the fold.

Thirty hashtags being permitted is not an argument for using thirty. Hashtag reach has declined steadily and Instagram’s own guidance has moved toward a handful of genuinely relevant tags. Four to six specific ones beat thirty generic ones.

Does alt text have a character limit?

Nobody outside Meta can tell you with confidence, and the "100 characters" figure repeated everywhere has no official source behind it — there is even a 2021 report that Meta removed alt-text length limits entirely.

Write for screen readers instead of for a limit. Around 125 characters is a sensible practical ceiling because several screen readers truncate near there, and one clear descriptive sentence per slide is what a blind or low-vision follower actually needs. Describe what is in the image and what it means, not "image of a chart".

Alt text is also read by search crawlers, which makes it one of the few genuine SEO surfaces on an Instagram post. Writing it per slide rather than leaving it blank costs a minute and is the least-contested accessibility win available.