📐 Aspect Ratio Calculator

An aspect ratio is the proportional relationship between the width and height of an image, video, or screen. It is expressed as two numbers separated by a colon, such as 16:9 or 4:3. The first number represents width and the second represents height. An aspect ratio describes the shape of a rectangle without specifying its actual size — a 1920×1080 screen and a 3840×2160 screen are both 16:9.

YouTube's standard video format is 16:9 with a recommended resolution of 1920×1080 (Full HD) or 3840×2160 (4K). For YouTube Shorts, use 9:16 vertical format at 1080×1920. YouTube automatically adds letterboxing (black bars) if your video does not match 16:9, so shooting in 16:9 gives the best viewing experience across devices.

Instagram supports three aspect ratios for feed posts — 1:1 (square, 1080×1080), 4:5 (portrait, 1080×1350), and 1.91:1 (landscape, 1080×566). For Stories and Reels, use 9:16 (1080×1920). The 4:5 portrait format is recommended for feed posts because it takes up the most screen space in the feed and typically gets higher engagement.

Divide both the width and height by their greatest common divisor (GCD). For example, 1920×1080: the GCD of 1920 and 1080 is 120. So 1920÷120=16 and 1080÷120=9, giving you a 16:9 ratio. This calculator handles this automatically — just enter your dimensions.

Common print aspect ratios are 3:2 (matches 6×4 inch prints and most DSLR sensors), 5:4 (matches 8×10 inch prints), and 4:3 (matches 6×4.5 inch prints). If your photo's aspect ratio does not match the print size, it will need to be cropped. Always check the target print dimensions before cropping.