How Do They Calculate Calories on Food Labels?

Do you ever find yourself standing in line at a coffee shop or restaurant with a large display board that lists all the available foods and beverages along with their calorie content, trying to decide if you really want the large size fries with 490 calories or whether the medium size with 320 calories will feel satisfying? Or asking yourself: How can a 16 ounce caramel macchiato have THAT many ca...