Aspect Ratio Calculator

This aspect ratio calculator keeps proportions intact when you resize. Set a ratio — or pick a preset like 16:9 — then type either the width or the height and the other dimension is filled in automatically. It also works in reverse: enter any pixel width and height and the calculator reduces them to the simplest whole-number ratio.

Aspect ratio is width divided by height. 16:9 is the standard for YouTube, streaming and almost every monitor sold today (1920×1080, 2560×1440, 3840×2160 are all 16:9). 9:16 is vertical video for TikTok, Reels and Shorts. 1:1 squares still dominate Instagram feed posts, 4:3 is the classic photo and older display ratio, and 21:9 is ultrawide cinema. Social preview images are 1.91:1 — 1200×630 pixels.

Getting this right matters because scaling to the wrong ratio either stretches the image or crops content you wanted to keep. Use this aspect ratio calculator before exporting from Figma, Premiere or Photoshop, when setting CSS aspect-ratio on a video container, or when a client asks for "the same banner but 1200 wide". Everything is calculated instantly in your browser — free, no signup.