Pizza Calculator

Quick Answer

Last updated: 10 November 2026 ·How we calculate this: circle area and price per square inch

How This Pizza Calculator Works

Pizza menus list sizes by diameter, but what you eat is area. Because area grows with the square of the diameter, a pizza that is a few inches wider can have far more pizza. Enter up to three sizes and prices. The calculator finds each pizza’s area and price per square inch, picks the best deal, and, if you enter the number of people, works out how many pizzas to order and what they cost.

How to Use the Pizza Calculator

1. Enter the diameter and price of two or three pizzas.
2. Enter how many people you are feeding.
3. Enter slices per person and slices per pizza.
4. Press Calculate.
5. Read the best deal, price per square inch and how many pizzas to order.

Pizza Formulas

• Area: π × (diameter ÷ 2)², with π ≈ 3.14159
• Price per square inch: price ÷ area
• How many times bigger: (larger diameter ÷ smaller diameter)²
• Slices needed: people × slices per person, rounded up
• Pizzas to order: slices needed ÷ slices per pizza, rounded up

Key Terms

• Diameter: the distance straight across the pizza through its center.
• Radius: half the diameter.
• Area: the size of the pizza’s surface, in square inches.
• Price per square inch: price divided by area; lower is better value.
• Pi (π): about 3.14159, the ratio of a circle’s circumference to its diameter.

Worked Example

A shop sells a 10-inch pizza for $9.99, a 14-inch for $15.99 and an 18-inch for $21.99.

• Areas: 78.5, 153.9 and 254.5 square inches
• Price per square inch: 12.72, 10.39 and 8.64 cents
• The 18-inch is the best deal and has 3.24 times the pizza of the 10-inch for about 2.2 times the price
• For 12 people eating 3 slices each from 8-slice pizzas: 36 slices, so 5 pizzas

Real-Life Examples

• Ordering: see if a large is worth the extra few dollars over a medium.
• Parties: 12 people eating 3 slices each need 5 eight-slice pizzas.
• Deals: compare two mediums for a set price against one extra-large.
• Math class: a tasty way to show that area grows with the square of the diameter.

One Large Pizza vs Two Medium Pizzas

• One 18-inch pizza: 254 square inches.
• Two 12-inch pizzas: 226 square inches, less than one 18-inch.
• Two 14-inch pizzas: 308 square inches, more than one 18-inch, so compare the prices.

Pizza Sizes Compared

Area includes the crust.

Things That Change the Real Value

Price per square inch is the fairest single number, but a few things change what you get. Crust is part of the area; a thick outer crust on a small pizza takes a bigger share of it. Deep-dish and thick-crust pizzas have more food per square inch than thin crust, so compare like with like. Toppings are often spread more thinly on large pizzas. Deals such as two-for-one or a free side can beat the per-square-inch math, so enter the effective price you would pay.

For parties, slice size matters as much as slice count. A 16-inch pizza cut into 8 slices has slices about 1.8 times as big as a 12-inch pizza cut into 8, so people eat fewer of them. Children usually eat 1 to 2 slices and adults 2 to 4. Ordering one extra pizza for every 10 to 15 people avoids running short.

Common Mistakes to Avoid

• Comparing diameters directly. A 16-inch is not 33% more than a 12-inch; it is 78% more.
• Using the radius as the size. Menus list diameter.
• Ignoring slice size. Large pizzas have bigger slices, so people eat fewer.
• Comparing different crusts. Deep dish has more food per square inch.
• Forgetting deals. Enter the actual price after any coupon.

Frequently Asked Questions

References & Sources