Once you know how much of each menu item you need to prepare, determine the food cost of each item by adding the cost of all of its ingredients. To cost a complex menu item with many components, first cost the recipe for each component. If time does not allow you to properly cost all recipes, at least calculate the cost of the main ingredients to project an approximate cost.
If food décor items that add to the cost of the buffet are included, determine their cost as well. For example, if you plan to decorate your buffet with a bread sculpture or fruit display, you must calculate its food cost in the same manner as the dishes that will be eaten.