How to Set the Right Aspect Ratio for Each Platform in Midjourney

Use the --ar parameter and a quick reference table to size images correctly for prints, social, and the web.

5 minBeginner

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Generating a square image and then cropping it for a vertical story wastes pixels and ruins composition. Midjourney can output almost any shape directly with the --ar parameter, so you should set the right aspect ratio before you generate, not after.

What you need

An active Midjourney subscription
The platform you are publishing to in mind
Your normal /imagine prompt

Step 1: Understand the --ar syntax

The parameter is --ar followed by width then a colon then height, for example --ar 16:9 for widescreen or --ar 9:16 for a vertical phone screen. It always goes at the end of the prompt with the other parameters.

aspect ratio

/imagine prompt: a neon city skyline at night --ar 9:16

Step 2: Match the ratio to the platform

Each destination has a preferred shape. Use this quick reference so your image fills the frame without awkward cropping.

Use case	Recommended --ar
Instagram square post	1:1
Instagram or TikTok story / reel	9:16
Instagram portrait feed post	4:5
YouTube thumbnail or banner	16:9
Desktop wallpaper	16:9
Pinterest pin	2:3
Print poster	2:3 or 3:4

Aspect ratio shapes

1:1 [ square ]

9:16 [ tall story ]

16:9 [ wide banner ]

4:5 [ portrait ]

Set the frame before generating, not by cropping later.

Step 3: Compose for the chosen shape

Add composition words that suit the ratio. For a 9:16 story, words like full-length and standing help the model fill the tall frame. For 16:9, phrases like wide establishing shot use the horizontal space well.

Extreme ratios can confuse the model

Very wide or very tall ratios like 21:9 sometimes cause repeated or stretched subjects. If that happens, generate at a milder ratio and use Pan to extend toward the extreme shape afterward.

Step 4: Verify before upscaling

Check that the grid came back in the shape you asked for and that the subject is not cut off. Only then upscale, so you do not spend Fast hours upscaling a badly framed image.

Result: an image that drops straight into your story, thumbnail, or print layout at the correct proportions, with the composition built for that shape from the start.