Work out the right pixel dimensions to keep an image or video in proportion. Set your target aspect ratio, such as 16:9 for widescreen video or 4:3 for classic photos, then type a width and the calculator fills in the matching height, or type a height to get the width. This saves you from squashed or stretched media when you resize, crop for a thumbnail, or plan a layout. You can also enter a custom ratio for anything unusual. Because it works both directions, you always land on the exact pair of dimensions that preserves the shape you want. It runs entirely in your browser with instant results as you type, so there is nothing to install and no waiting, and none of your values are ever sent anywhere.