Chefs use yield percentages to determine how much to charge for menu items, the quantity of products to order and how many servings a recipe produces. Extraneous factors, such as the skill level of the cook preparing the item, influence an item's yield percentage. For instance, a yield percentage increases in tandem with a cook's proficiency because she produces less waste (or yields more usable product) due to precise knife cuts. The quotient derived from dividing the edible portion quantity (EPQ) of an item by its as purchased quantity (APQ) equals a product's yield percentage. For example, if a chef has eight pounds of usable product remaining after trimming and de-boning a 10-pound chicken, she achieved an 80 percent yield.
Cooks use the inverse properties of division to convert ingredients between units of measurement. For instance, to convert 32 ounces to pounds, a chef turns the pre-conversion quantity (32) into a fraction by placing the number one under it (32/1). He makes another fraction by placing the number of ounces in a pound under the number one (1/16). The product of the two fractions equals the number of ounces in pounds (32/1 x 1/16 = 2).
Chefs convert whole numbers to percentages regularly to determine food costs, labor costs and profit. This is done by dividing parts of a whole by 100 then moving the decimal point two places to the right (34/100 = 0.34 = 34 percent).
Fractions and percentages are used when converting recipes. Simple fractions are created by placing a whole number over one (16 = 16/1), or taking a percentage and moving the decimal two places to the left (34 percent = 0.34 = 34/100).
Calculating food costs is integral to determining a kitchen's solvency and profitability. A chef first adds the kitchen's beginning food inventory (BI) with its purchases (P). She then subtracts the ending food inventory (EI) and divides the total sum by the amount in food sales produced by the kitchen. The quotient equals the food cost percentage for that week (20,000 + 5,000 - 18,000/30,000 = 7/30, or 25 percent). Most chefs set a weekly food cost percentage goal between 30 and 40 percent of total sales.