In this video it is explained the term: aspect ratio. What means aspect ratio, an how it is calculated. How aspect ratio will help you, and in what situations. You have two options, to calculate aspect ratio by formula, or calculate aspect ratio very quick with aspect ratio calculator from here: http://www.ninjaunits.com/aspect-ratio-calculator/ It's your choice, but I highly recommend to use the second method to calculate aspect ratio by calculator, because it is the quickest way to do that and very accurate.