Oh, you'll need a whole lot more than 50sq ft to do your whole car. There's pretty much no limit to how much damping mats you can apply onto a car, up until the panels don't fit anymore.
In reasonable terms, a single door can take about 15~20sq ft (inner and outer panels). The floor will take a whole lot more, the roof will not take as much as you'd expect, and the boot would again be quite a bit.
If you want to go all out, buy about 200sq ft of damping mats and see where that takes you. It's always better to have a lil extra to apply double layers elsewhere, rather than to fall short in the middle of working on it.
Lastly, there's no reason for you to choose dynamat, cause there are a whole lot more companies you can choose from that are cheaper and give similar, if not superior performance. unless you're sponsored by Dynamat. In which case, you wouldn't have asked this question, so I'm going out on a limb here to say you're not.
Look into other makers.//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif