Pizza Calculator

The catering planner default is 3 slices per adult. A 14 inch large pizza serves 3 to 4 adults at that rate (it carries 10 slices). For a quick mental check, divide the head count by 3 and round up: 12 people need 4 large pizzas, 20 people need about 7. Bump up to 4 slices per person for hearty appetites, game day, or late-night ordering, and down to 2 for kids' parties or when pizza is a side rather than the main course.

US pizza chains use a fairly consistent slice count: 10 inch small cuts into 6 slices, 12 inch medium into 8, 14 inch large into 10, 16 inch XL into 12, and 18 inch XXL into 14. Independent shops vary by a slice or two, but the totals are close enough that the calculator's pizzasNeeded figure is reliable for ordering. If your local shop cuts an 18 inch into 16 slices instead of 14, the order is still right because you are paying per pizza, not per slice.

Larger pizzas almost always win on cost per slice because the price scales with diameter, not area. A 14 inch large has roughly 1.96 times the surface area of a 10 inch small (154 vs 78 square inches), but rarely costs twice as much. For groups of 6 or more, two large pizzas beat three or four smalls on both price and leftovers. The calculator's cost-per-person field makes this easy to compare across sizes when you have a menu open.

When you turn on the kids half-portion mode, each kid in the kidsCount field counts as half an adult for the slice calculation. So 8 adults plus 4 kids at the average appetite (3 slices each) becomes (8 * 3) + (4 * 1.5) = 30 slices, not 36. With the toggle off, kids count as full adults so you can pad up for picky eaters or hungry teens. The kid count cannot exceed the total head count because kids are part of, not on top of, the guest list.

A medium hand-tossed cheese slice runs about 250 to 320 kcal across the major US chains. The calculator uses 285 kcal as the midpoint. Pepperoni adds roughly 15 to 30 kcal per slice, sausage and bacon push that to 30 to 50, and loaded supreme or stuffed-crust pies can top 350 to 450 kcal per slice. Three slices of plain cheese sit around 855 kcal, which is a substantial single meal but well within a typical 2,000 kcal daily target.