They both hold 20 cups of popcorn, but the large tub looks a lot larger than the medium bag. Oh, and if you want to add some of that “buttery topping,” that contains about 120 calories per tablespoon. At AMC, a small popcorn contains 370 calories, with the saturated fat equivalent of about eight pats of butter. Medium contains 590 calories and 33 grams of saturated fat, and a large popcorn contains 1,030 calories, with 57 grams of saturated fat. As for Cinemark, their small-size popcorn contains 400 calories, the medium contains 760 calories, and the large 910.