Aspect ratio is the proportion of an image's width to its height, usually expressed as two integers separated by a colon. A 16:9 image is 16 units wide for every 9 units tall — the standard for video and most computer displays. 4:3 is the older television standard, still common for product photos. 1:1 is square (Instagram grid). 9:16 is vertical (Instagram Stories, TikTok). 3:2 is the photographic 35mm-film standard, common for print.
For architectural rendering, aspect ratio choice depends heavily on where the render will live. Portfolio prints favor 3:2 or 4:5; web heroes favor 16:9 or wider (21:9 cinematic); Instagram grid wants 1:1 or 4:5; LinkedIn posts work best at 1.91:1; vertical social formats need 9:16. The choice also shapes what composition strategies work — a wide aspect ratio favors landscape exteriors and long interiors; a tall aspect ratio favors tower architecture or single-figure portraits.
AI rendering supports any aspect ratio you specify. Most platforms expose preset ratios (16:9, 4:5, 1:1, 9:16) and many also support arbitrary custom dimensions. When composing the prompt, keep in mind that the composition advice ('centered one-point perspective', 'rule of thirds') interacts with the aspect ratio — a 1:1 render will frame the same scene quite differently than a 16:9 of the same prompt.
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