Pizza Size Calculator

What this does

So you are staring at a menu wondering whether the large is really worth the extra few dollars, or whether two mediums beat one big one. This calculator cuts through it. Enter a pizza's diameter and it gives you the actual surface area, the true measure of how much pizza you are getting, so you can compare sizes honestly before you order.

How to use it

1. Enter the diameter of the pizza.
2. Press Calculate to see the surface area in square units.

Work out the area for each size you are weighing up, then compare them against their prices.

How the maths works

A pizza is a circle, and the area of a circle comes from its radius, which is half the diameter:

area = π × (diameter ÷ 2)^2

So a 16 inch pizza has an area of π times 8 squared, which is about 201 square inches. The diameter you read off the menu is just the width, but the area is what actually feeds people, and it can differ from the number on the box in a way that really matters.

The insight that saves money

Here is the part worth knowing. Because area depends on the square of the diameter, a small jump in width is a big jump in pizza. Double the diameter and you do not get twice the pizza, you get four times as much.

That flips a lot of orders on their head. One 18 inch pizza, at about 254 square inches, actually beats two 12 inch pizzas, which come to roughly 226 square inches between them, and it is usually cheaper too. So rather than counting pizzas, work out the area, divide it by the price, and order whatever gives you the most pizza per dollar. The bigger pie wins far more often than people expect.

Questions people ask