We suspect you don’t really need another reason to buy a bigger pizza.

But if you do, here’s a great one: You’ll get more pizza for your money if you go with the larger pie.

Quoctrung Bui of Planet Money recently studied this after noticing something while eating lunch with an engineer.

Though the engineer claimed not to be very hungry, he ordered the 12-inch medium pizza instead of the 8-inch small. His reasoning: The medium was more than twice as big as the small and only cost a bit more.

The math of why the bigger pizza is a better deal is straightforward. The area of a circle, the pizza in this case, increases with the square of the radius.

In other words, the bigger the pizza, the larger the radius and the more pizza you get for a small price difference. (In case you’ve forgotten, the area of a circle is Pi (3.14) times the radius squared.)

Bui downloaded the price of 74,476 pizzas from 3,678 restaurants around the country to come up with average comparisons, such as this one for a 16-inch pizza.

The advantage of ordering large is even more striking for a 20-inch pie.

Don’t miss the fantastic interactive infographic ^{[3]} that Bui created to fully demonstrate the pizza phenomena.

Of course we don’t expect you to eat all of that extra cheese and pepperoni at once.

True to the Bargaineering spirit, we think you should take the extra home and freeze it. All you have to do is pop it in the microwave and it’s nearly as good as new.

The zip lock bags you buy to store the pizza will add some expense, but that cost is marginal compared to what you save by purchasing the larger pie.