What it does
An aspect ratio, pixel pitch and display geometry calculator that runs entirely in the browser. Resolution × pixel pitch = physical size, so any two of the three give the third — and it names the ratio the way the trade does, telling you that 3440×1440 is 21:9 rather than 43:18, and that 1366×768 is 0.049% off 16:9 rather than pretending it is exact. It sizes PowerPoint slides on the same arithmetic, working around the 56-inch slide limit and pointing out when the better answer is to leave the deck alone and raise the export DPI.