Aspect Ratio Calculator

About this calculator

An aspect ratio is the ratio between a shape’s width and height, reduced to its simplest whole-number form the same way you would simplify a fraction — by dividing both numbers by their greatest common divisor. A 1920×1080 image, for instance, reduces to the familiar 16:9, while 1080×1080 reduces to 1:1 and 2560×1080 lands on the ultrawide 21:9.

Video editors, photographers and app designers rely on aspect ratio constantly: choosing 16:9 for YouTube and most TVs, 9:16 for Instagram Reels and TikTok, 4:3 for older broadcast and some print formats, or 21:9 for cinematic widescreen. Getting the ratio right before you crop or export avoids black bars, stretched footage or awkward re-cropping later.

This calculator takes any pixel width and height, reduces them with the same divisor logic, and also gives you the decimal ratio so you can compare dimensions that do not simplify to a clean whole-number pair.