Calculate and scale aspect ratios for images and video.
An aspect ratio is the proportional relationship between width and height, written as two numbers such as 16:9. It tells you the shape of a screen, photo or video independent of its size. Enter a width and height to find the simplified ratio, or enter a ratio and one side to find the missing dimension.
To simplify, divide both numbers by their greatest common divisor. For 1920 × 1080 the common divisor is 120, giving 16:9. To resize, use new height = new width × original height ÷ original width. Scaling 1920 × 1080 to a width of 1280 gives a height of 1280 × 1080 ÷ 1920 = 720.
Keep the ratio locked when resizing, otherwise images look stretched or squashed. When you must change the shape, crop instead of stretching.