AI Image Aspect Ratio Guide — Which Ratio for Which Use

Different platforms need different aspect ratios. Pick the right ratio before you generate to avoid awkward crops — and learn which models support which ratios natively.

Every AI image model supports a handful of aspect ratios, but each platform has its own ideal. Generating a square image for a YouTube thumbnail or a 16:9 image for a Pinterest pin wastes credits and produces awkward crops. This page is a quick reference for which ratio fits each common platform and which AI models handle non-square ratios best.

When to use it

Common ratios: 1:1 (Instagram square), 4:5 (Instagram portrait), 9:16 (TikTok, Reels, Stories), 16:9 (YouTube thumbnails, presentation slides, blog hero images), 3:4 (magazine portrait), 21:9 (cinematic widescreen). Midjourney's --ar flag accepts any custom ratio. Imagen 4 and Flux 2 also support arbitrary ratios. Stable Diffusion works best at 512x512 multiples — non-standard ratios sometimes need ControlNet to avoid composition drift.

AI Image Aspect Ratio Guide — Which Ratio for Which Use

When to use it

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