Free AI Image Size Tool

AI Aspect Ratio Cheat Sheet

Pick what you are making. Get the exact aspect ratio and pixel size, plus the copy-paste syntax for Midjourney, DALL-E, Stable Diffusion, FLUX and Nano Banana. Free, no signup.

1. Pick your use case
1:1
Instagram Post
1:1
1080 × 1080 px
Square
DALL-E 3 only makes three sizes: 1024x1024, 1024x1792 and 1792x1024. For any other shape, generate the nearest size and crop to your ratio. Midjourney, Stable Diffusion and FLUX hit any ratio exactly.
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Nail the ratio, then nail the prompt

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Reverse lookup: every common ratio

Already know your ratio? Here is what each one is for and how to type it in Midjourney.
RatioShapeBest forMidjourney
1:1SquareInstagram post, avatars, album and podcast art--ar 1:1
4:5PortraitInstagram feed portrait (takes up more screen)--ar 4:5
2:3PortraitPinterest pins, art prints, photo posters--ar 2:3
3:4PortraitPoster prints, book pages, tablet screens--ar 3:4
5:8TallEbook and book covers (1:1.6 standard)--ar 5:8
9:16Tall verticalStories, Reels, TikTok, YouTube Shorts--ar 9:16
9:20Tall verticalPhone wallpaper (modern edge-to-edge screens)--ar 9:20
16:9WidescreenYouTube, desktop wallpaper, slides, X posts--ar 16:9
3:2LandscapeDSLR photography, classic prints--ar 3:2
21:9Ultra-wideCinematic shots, ultrawide monitors--ar 21:9
1.91:1WideFacebook, LinkedIn and X link previews (OG image)--ar 191:100
3:1BannerX (Twitter) header--ar 3:1
4:1BannerLinkedIn profile banner--ar 4:1

How it works

No math, no signup, nothing leaves your browser.
1. Pick your use caseTap Instagram, YouTube, a wallpaper, a poster, a book cover, anything on the list.
2. See the ratio and sizeThe exact aspect ratio and pixel size, drawn to scale so you know the shape you are getting.
3. Copy for your modelOne tap copies the right syntax for Midjourney, DALL-E, Stable Diffusion, FLUX or Nano Banana.

Questions

What aspect ratio should I use for Instagram, YouTube and TikTok?
Instagram posts are 1:1 (1080x1080) or 4:5 (1080x1350). Instagram Stories, Reels, TikTok and YouTube Shorts are all 9:16 (1080x1920). YouTube videos are 16:9 (1920x1080) and thumbnails are 16:9 (1280x720). Pick the use case above and it fills in the exact numbers.
How do I set the aspect ratio in Midjourney?
Add the --ar flag with whole numbers at the end of your prompt, like --ar 16:9 for widescreen or --ar 9:16 for vertical. Midjourney only accepts whole-number ratios, so use 191:100 instead of 1.91:1.
Does DALL-E 3 support custom aspect ratios?
No. DALL-E 3 only outputs three sizes: 1024x1024 (square), 1024x1792 (portrait) and 1792x1024 (landscape). Pick the closest one and crop to your exact ratio. Midjourney, Stable Diffusion and FLUX give you any ratio you want.
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