Key takeaways
- Design at the shape the platform shows: 4:5 (1080×1350) is the common Instagram feed choice, 9:16 for Reels and Stories, 2:3 for Pinterest.
- Instagram’s profile grid previews posts at 3:4, so keep key content centred (per Buffer’s Instagram size guide).
- Text needs a contrast ratio of at least 4.5:1 (3:1 for large text) to meet the W3C’s WCAG 2.2 guideline.
- Alt text can be added in SkedCast for X (Twitter), LinkedIn, Instagram, Facebook Pages, Threads, Bluesky.
What size should a social media post be?
These are the shapes SkedCast’s composer recommends and the file rules it enforces per platform, read from the same rulebook the publishing adapters use — so an image that passes here will not be rejected at publish time. Exact pixel sizes are on each platform’s image-size page.
| Platform | Recommended shapes | Formats | Max file size | Images per post | Pixel sizes |
|---|---|---|---|---|---|
| X (Twitter) | 16:9, 1:1 | jpeg, png, webp, gif | 5 MB | 4 | X (Twitter) image sizes |
| 1:1, 4:5, 1.91:1 | jpeg, png, gif | 5 MB | 20 | LinkedIn image sizes | |
| 1:1, 4:5, 1.91:1 | jpeg | 8 MB | 10 | Instagram image sizes | |
| Facebook Pages | 1:1, 4:5, 1.91:1 | jpeg, png | 10 MB | 10 | Facebook Pages image sizes |
| TikTok | 9:16 | jpeg, webp, png | — | 35 | TikTok image sizes |
| YouTube | Video-only platform — no image posts | — | — | — | YouTube image sizes |
| Threads | 1:1, 4:5 | jpeg, png | 8 MB | 20 | Threads image sizes |
| 2:3 | jpeg, png | 20 MB | 5 | Pinterest image sizes | |
| Bluesky | 1:1, 4:5, 16:9, 1.91:1 | jpeg, png, webp | 1 MB | 4 | Bluesky image sizes |
| Telegram | Native (shown as sent) | jpeg, png | 10 MB | 10 | Telegram image sizes |
What are the Instagram sizes to design for?
Buffer’s 2026 Instagram size guide lists feed posts as square (1080×1080), portrait (1080×1350) or landscape (1080×566), Stories and Reels at 1080×1920 (9:16), and notes that the profile grid displays every post at a 3:4 ratio. The practical rule is to design in 4:5 and keep the important content in the centre so it survives the grid crop. SkedCast’s Instagram adapter accepts JPEG; PNG and WebP are converted.
What are the design basics that make a post work?
Five checks, in the order that usually matters:
- One idea per image. If it needs a paragraph, it is a carousel or a caption.
- Legible at phone size. Preview the design small; body text that is not readable at thumbnail size will not be read in the feed.
- Sufficient contrast. The W3C’s WCAG 2.2 success criterion 1.4.3 asks for at least 4.5:1 between text and its background, or 3:1 for large text (18 pt or 14 pt bold and above).
- Safe zones. Keep text and faces away from the edges, where crops, the profile-grid preview and the app’s own buttons and captions cover the image.
- A consistent template. A repeatable set of layouts, colours and fonts makes posts recognisable and faster to produce.
How do carousels and multi-image posts differ by platform?
The number of images one post can carry differs widely, so a carousel designed for one platform may not fit another as it stands. These are the per-post media ceilings SkedCast enforces.
| Platform | Max media items per post |
|---|---|
| X (Twitter) | 4 |
| 20 | |
| 10 | |
| Facebook Pages | 10 |
| TikTok | 35 |
| YouTube | 1 |
| Threads | 20 |
| 5 | |
| Bluesky | 4 |
| Telegram | 10 |
What are some social media post design ideas?
Formats to start from, each with a job to do:
- Quote or stat card: one sentence or one number, large, on a plain background.
- Carousel walkthrough: one step per slide with a cover slide that states the promise.
- Before and after: two panels showing a change; label both.
- Checklist: a short list people will save; keep it to what fits at phone size.
- Behind the scenes: a real photo with a short caption, which needs less design than the others.
- Announcement: date, place or offer first, then the detail.
- Data snapshot: one chart with one takeaway in the headline.
How do alt text and captions fit in?
Alt text describes an image for people who cannot see it, and it can be set per image when you schedule on X (Twitter), LinkedIn, Instagram, Facebook Pages, Threads, Bluesky. Put text that matters in the caption as well as in the image, because text baked into an image is invisible to screen readers and to search. The free alt text generator drafts descriptions to edit.
How do you get from a finished design to a scheduled post?
Export at the platform’s shape and a supported format, upload it once to SkedCast’s media library, and attach it in the composer to as many platforms as fit; where one image cannot serve all, add a platform-specific media set for that variant. SkedCast is a scheduler and publisher, not an image editor, so design in the tool you already use and bring in the finished file — see how to schedule posts from Canva.
Sources
FAQ
- What is the best size for a social media post?
- It depends on the platform. For Instagram a 4:5 (1080×1350) portrait image is the common choice, 9:16 suits Reels and Stories, and Pinterest favours 2:3. The table above lists the shapes and file rules SkedCast enforces for every platform.
- Why is my Instagram post cropped on my profile?
- Instagram’s profile grid previews every post at a 3:4 ratio, so anything near the edges of a 4:5 or square image can be cut off in the grid. Keep key content centred.
- What contrast ratio should text on a post have?
- The W3C’s WCAG 2.2 criterion 1.4.3 asks for at least 4.5:1 for normal text and 3:1 for large text (18 pt or 14 pt bold and above).
- How many images can a post have?
- It varies by platform: for example Instagram and Facebook 10, LinkedIn and Threads 20, TikTok 35 and X 4 in SkedCast’s composer. See the carousel table above.
- Does SkedCast design or edit images?
- No. SkedCast schedules and publishes; design and edit images in your usual tool, then upload the finished file.