People elsewhere on the forum have mentioned some side effects they've experienced in their beers due to overpitching - hot fusel alcohols that give a burning sensation to the beer, and bitter yeast-bit are the two most common. Not everyone experiences this, though.
All I'm saying is this: we choose specific yeast for certain flavor characteristics. We say that California Ale is a clean fermenting ale producing mild fruitiness, and London ESB ale is less attenuative with a maltier emphasis. But all these descriptions are based off of proper pitching rates that yeast manufacturers recommend, that breweries follow, and that professional brewers and highly experienced homebrewers stand by without question. So do what you want, but just know that you are deliberately ignoring the knowledge and experience that professionals have gained through countless experiments.
And before you think I'm on too high of a horse (which I admit), when I started out brewing I was definitely in the "who cares?" category when it came to yeast. I fermented at whatever temperature and I never made a starter. Then I had a few terrible batches that I directly attribute to poor yeast management. Now I really pay attention to what I'm doing with my yeast. As homebrewers we get excited about this ability to pick out our malts and hops, and think that we're really creating something unique with each recipe. But what we provide beer in terms of ingredients is nothing compared to what yeast provide through fermentation. So respect 'em!
Use the calculator, and save some of that sweet cake that your yeast worked so hard to produce for some more beers!