AI Image Aspect Ratios: Which Size for Instagram, YouTube and Print?

4 min read · Updated 04 Oct 2026 · By the Picslot team

The aspect ratio you choose changes composition, not just the crop. A tall portrait and a wide landscape lead the model to arrange the scene differently, so pick the ratio before you generate rather than cropping afterward.

1:1 square

Square images suit profile pictures, album covers, logos and product tiles. They work well for centered subjects and symmetrical designs.

4:5 and 9:16 vertical

4:5 is a popular portrait shape for social feeds and gives a subject more height without feeling extreme. 9:16 matches phone screens and is the standard for stories and short videos. Vertical frames suit full-body characters and tall buildings.

16:9 and 21:9 wide

16:9 matches video, presentations and most monitors, so it is the usual choice for YouTube thumbnails, banners and desktop wallpapers. 21:9 is a cinematic ultrawide ratio, ideal for landscapes, space scenes and film-still looks.

3:2 photographic

3:2 is the classic ratio of many cameras. It is a good default for realistic photography prompts and prints.

How to set it

In Midjourney use the "--ar" parameter, for example "--ar 16:9". Other tools offer ratio presets or width and height fields. The Image to Prompt tool suggests the closest ratio for any picture and adds the right flag to its Midjourney prompt.

Browse Explore and filter by aspect ratio to see how other creators compose for each format.