This aspect ratio calculator does the two jobs that come up when working with screen, image and video dimensions: it simplifies a width and height into a clean ratio, and it resizes a width or height while keeping a chosen ratio so nothing gets stretched. An aspect ratio is just the proportion of width to height, written like 16:9 or 4:3, and it describes the shape of a display, photo or video independent of its actual pixel size. The first tool takes any width and height and reduces them to their simplest whole-number ratio by dividing both by their greatest common divisor, also showing the decimal ratio, so 1920 by 1080 comes out as 16:9. The second tool keeps a target ratio fixed: enter the ratio, such as 16 and 9, then type a new width to get the matching height, or a new height to get the matching width, which is exactly what you need when scaling an image or laying out a video frame without distortion. Common ratios worth knowing are 16:9 for video and most screens, 4:3 for older displays, 3:2 for many cameras, 1:1 for square social posts and 21:9 for ultrawide. The results update as you type. Enter your dimensions to simplify a ratio or resize while keeping the shape.
To simplify, the calculator divides the width and height by their greatest common divisor, leaving the smallest whole-number ratio, and also shows the decimal form. To resize, it uses the fixed ratio: a new height is the new width times the ratio height divided by the ratio width, and a new width is the new height times the ratio width divided by the ratio height. Type into the width or the height to drive the other.
A 1920 by 1080 image simplifies to 16:9, since both divide by 120. Keeping 16:9, a new width of 1280 gives a height of 1280 times 9 over 16, which is 720, so the resized frame is 1280 by 720.
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