A Costco pizza has exactly 12 slices. Each pizza is 18 inches in diameter and is cut into 12 uniform slices, made by first cutting into 6 large slices and then halving each one. The pizza is available in two main types: cheese and pepperoni. A single Costco pizza can typically feed about 3 to 5 people depending on appetites. The whole pizza costs around $9.95, making the cost per slice roughly 80 cents if bought as a whole pie.