How many calories are in 1 McDonald's Filet-O-Fish sandwich?!
It's 380 calories, including the cheese and tartar sauce.
Here's a link to the filet-o-fish nutrition page on McDonald's website (you can click on the boxes next to "cheese" and "tartar sauce" and then click "recalculate" if you want to know the calories without them):
It's only 290 calories without the tartar sauce, by the way.
You can find out by looking at the McDonald's posting in the restaurant, or on the sandwich package itself. Possibly, just looking at McDonald's website might be what anyone would do.
All nutritional information is available on their website, but to be honest if your worried about calories, macdonalds is not the greatest idea :-/
380 according to the McDonalds nutrition guide.