The number of calories in movie theater popcorn varies based on the theater and the size of the popcorn. At Regal Entertainment Group, which is the most common movie theater chain found in the United States, a small popcorn has 670 calories, and a medium/large size contains 1,200 calories.
At AMC Theatres, the second largest American movie chain, the small, medium and large servings of popcorn contain 370, 590 and 1,030 calories, respectively. Cinemark, the third most popular movie theater chain in the nation, does not offer a small popcorn. Its medium popcorn has 760 calories, and the large has 910 calories.