Aspect Ratio Calculator
Reduce a ratio or find a missing dimension
Frequently Asked Questions
The width and height are divided by their greatest common divisor (GCD), reducing them to the smallest whole numbers with the same proportion — e.g. 1920x1080 reduces to 16:9.
Multiply the known dimension's ratio partner: if you know the width and want the height, height = width × (ratio height ÷ ratio width).
16:9 is standard HD/4K video, 9:16 is vertical video (Reels/Shorts/Stories), 4:3 is classic TV, 1:1 is square, and 21:9 is ultrawide cinema.
Most video codecs (H.264, H.265) require even pixel dimensions to encode properly. Round your result up to the nearest even number if you're exporting video.