Pizza calculator

How many pizzas to order for a party. Enter your kids and grown-ups; the answer updates as you type.

Festidy's plan uses the same amounts and updates them as RSVPs come in.

How we calculate

Kids: 2 slices each, or 1.5 when most are 5 and under.
Grown-ups: 3 slices each.
Pizzas: all the slices divided by the slices in a pizza, rounded up. A large pizza (14 inches) is usually cut in 8.
Toppings: about half the kids' pizzas plain cheese and half pepperoni; for grown-ups, one in three with veggies.
Cost: about $12 to $18 for a large pizza from a chain, before delivery and tip.

Last updated October 21, 2026. Free, no sign-up.

New to Festidy? See how the free birthday party planner works.

Order for the time you eat, not the time guests arrive. Ask for delivery 15 minutes before snack time in your schedule.
Cut kids' slices in half. Small hands waste less, and the same pizza feeds more.
Ask about allergies first. Festidy's RSVP asks guests for allergies, so you know before you order.
Leftovers are fine. One extra pizza costs less than running out.

How many pizzas for 20 kids?

About 5 large pizzas for 20 kids aged 6 and up (40 slices), or 4 if most are 5 and under. Add 1 more for every 3 grown-ups who eat.

How many slices of pizza does a child eat?

Most kids eat 2 slices at a party, and kids 5 and under about 1.5. Party food, cake and excitement mean they eat less than at dinner.

How many pizzas for 15 people?

For 9 kids and 6 grown-ups (a typical kids' party mix), 5 large pizzas: 18 slices for the kids and 18 for the grown-ups.

What size pizza should I order for a party?

Large pizzas (about 14 inches, 8 slices) are the best value for a crowd. Extra-large pizzas are cheaper per slice but floppy for small kids.