AI Image Size Guide
Which resolution and aspect ratio to use for AI-generated wallpapers, social posts, print and web images, in one practical reference.
Start with aspect ratio, not resolution
Aspect ratio (the shape) and resolution (the pixel count) are two separate decisions, and getting the ratio right first matters more, because most AI models will crop or letterbox a mismatched ratio rather than intelligently reframe it. Decide your ratio using the Aspect Ratio Calculator before you worry about final pixel dimensions.
Desktop & phone wallpapers
For desktop wallpapers, 16:9 is the safest default, generated at 1920×1080 (Full HD) or 3840×2160 (4K) if your model supports high-resolution output or upscaling. For phone wallpapers, 9:16 at 1080×1920 covers the vast majority of modern phone screens.
Social media images
Instagram feed posts work best square (1080×1080) or portrait (1080×1350, a 4:5 ratio), since Instagram's algorithm favors portrait posts for taking up more feed space. Stories, Reels and TikTok all use 9:16 at 1080×1920. YouTube thumbnails should be 16:9 at 1280×720.
Print needs meaningfully higher resolution than screen use — aim for 300 pixels per inch at your final print size. A standard 8×10 inch print needs 2400×3000 pixels; a 4×6 inch print needs 1200×1800 pixels. Use the print size table on the Aspect Ratio Calculator to get exact pixel requirements for any ratio.
Matching your AI generator's native output
Most AI image generators have a native output resolution lower than these final targets (often 1024×1024 or similar), relying on a separate upscale step for anything larger. Always check your specific model's documentation for its native resolution and maximum supported upscale factor before committing to a final size.