How aspect ratio calculator works
An aspect ratio is the proportional relationship between an image or screen's width and height, written as width:height. 16:9 means the width is 16 units for every 9 units of height. Reducing a resolution like 1920×1080 to 16:9 makes the proportions easy to compare and to scale.
This calculator divides both dimensions by their greatest common divisor to get the simplest integer ratio. 1920 and 1080 share a GCD of 120, giving 16:9. It also recognises common named formats (16:9 widescreen, 9:16 vertical, 4:3, 1:1 square, 21:9 ultrawide, and others) and reports the decimal ratio (width ÷ height).
Enter a width and height and the tool returns the simplified ratio, the named format if it matches one, and the decimal ratio. Use it when resizing images, picking video resolutions, designing slides, or matching a layout to a target screen.