Aspect Ratio Guide

What aspect ratio actually means

Aspect ratio describes the proportional relationship between an image's width and height, written as two numbers like 16:9 or 1:1. It's independent of resolution: a 1920×1080 image and a 3840×2160 image are both 16:9, just at different pixel densities. Changing the ratio changes the shape; changing the resolution changes the detail/sharpness at that shape.

Common ratios and what they're for

1:1 (square) is the most flexible and the default for most AI generators and Instagram posts. 16:9 is standard widescreen for monitors, TVs and YouTube. 9:16 is the vertical mirror of 16:9, used for phone wallpapers and Stories/Reels/TikTok. 4:5 is Instagram's recommended portrait post ratio. 3:2 is the classic 35mm photography ratio behind most standard print sizes.

How to convert between ratio and pixels

To go from a ratio to exact pixels, pick a target for one dimension (say, the longest edge) and scale the other dimension proportionally. For 16:9 at a 1920px long edge, the short edge is 1920 × 9/16 = 1080px. Rather than doing this by hand, use the Aspect Ratio Calculator, which does this instantly for any custom ratio, including AI generation, wallpaper and print-ready sizes.

Choosing a ratio for AI image generation

For AI art specifically, also consider that some models (like Midjourney) accept an explicit --ar parameter, while others require exact pixel dimensions as input. Check the Midjourney Aspect Ratio Calculator for a ready-to-copy --ar parameter, or the general calculator for exact pixel values if your tool needs raw dimensions instead.