Midjourney Aspect Ratios: The Right --ar for Every Platform

How --ar works

The aspect ratio is the relationship between an image's width and height. In Midjourney you set it with --aspect or its short form --ar at the end of the prompt:

a cyclist crossing a misty bridge at dawn, cinematic wide shot --ar 16:9

Three things to know:

• Width comes first. --ar 16:9 is landscape; --ar 9:16 is portrait.
• Whole numbers only. --ar 1.91:1 won't work, but --ar 191:100 will.
• The ratio changes the composition, not just the crop. Midjourney arranges the subject, background and empty space to suit the canvas. A tall ratio gives room for a full-length figure; a wide one invites landscapes and side-by-side layouts.

Without --ar, you get a square image.

Aspect ratios by platform and use

Platforms change their recommended sizes from time to time, so treat this as a starting point and check the platform's own guidance for pixel dimensions.

Designing for the format

Getting the ratio right is only half the job. The prompt should suit the shape too.

Vertical formats (9:16, 4:5, 2:3)

Describe things that are naturally tall: a full-length figure, a tall building, a waterfall, a bottle shot from slightly below. Mention where the subject sits, e.g. "subject in the lower third, open sky above" if you need room for text.

full-length portrait of a woman in a long camel coat walking down a narrow cobbled street, overcast light --ar 9:16

Wide formats (16:9, 3:1, 4:1, 21:9)

Describe horizontal scenes and use space deliberately. For banners, ask for the subject on one side and "negative space" on the other.

a single sailing boat on the far right of a calm grey sea, vast empty sky, minimal, plenty of negative space on the left --ar 4:1

Square (1:1)

Square suits centred, symmetrical subjects: a product, a face, a logo-like icon. Note that Midjourney isn't reliable at rendering long, exact text, so design the wording of any logo or banner separately.

Choosing between similar ratios

Some ratios are close enough that the choice comes down to how the image will be used.

• 4:5 or 1:1 for Instagram? 4:5 takes up more vertical space in the feed, which suits people, products and fashion. 1:1 is safer if the image also needs to work as a square thumbnail elsewhere.
• 2:3 or 4:5 for portraits? 2:3 gives more room above and below the subject, useful for full-length figures and posters. 4:5 is tighter and suits head-and-shoulders framing.
• 16:9 or 21:9 for headers? 16:9 is the safer all-rounder. 21:9 feels more cinematic but leaves less height for the subject, so it works best for landscapes and wide scenes.
• 3:2 or 16:9 for landscape photos? 3:2 feels like a classic camera frame. 16:9 feels like a video still.

When in doubt, generate at the ratio of the most important placement, then create separate versions for the others using the same prompt and seed so the family of images still feels consistent.

Practical tips for aspect ratios

1. Decide the destination first. If an image needs to work as both a 4:5 post and a 9:16 story, generate each separately rather than cropping one.
2. Use Pan or Zoom Out to extend. If you love an image but need a different shape, Midjourney's pan and zoom-out tools can extend the canvas in a direction.
3. Be careful with extreme ratios. Very wide or very tall ratios can produce stretched or repeated elements. If results look odd, try a slightly less extreme ratio and crop.
4. Upscale before printing. Midjourney's output size depends on the ratio and model. For large prints, upscale first and check the pixel dimensions against your printer's requirements.
5. Keep the ratio when testing. Changing --ar changes the composition, so keep it fixed when comparing other settings like stylize, chaos and weird.

For the full list of settings that sit alongside --ar, see Midjourney parameters explained.

Doing this faster with Dreamdrive

Dreamtune includes Composition and Technical dropdowns, so you can choose framing and format settings without remembering the syntax. My Prompts saves each prompt with its ratio into project folders, which makes it easy to rerun a campaign in every format you need.

Frequently asked questions