Most of us tend to order a pizza based on the amount we plan to eat—and there’s nothing wrong with that—but if you’re trying to make your dollar stretch as far as it can, your best bet is to just order the biggest one you can buy. Why? The increase in size to cost always comes out in your favor. Here’s why.

Over at NPR’s Planet Money blog, Quoctrung Bui explains:

One day last year, an engineer and I went to a pizza place for lunch. The engineer told me he wasn’t very hungry, but he said he was going to get the 12-inch medium instead of the 8-inch small — because the medium was more than twice as big as the small, and it cost only a little bit more. This sort of blew my mind.

…The math of why bigger pizzas are such a good deal is simple: A pizza is a circle, and the area of a circle increases with the square of the radius.

So, for example, a 16-inch pizza is actually four times as big as an 8-inch pizza.

And when you look at thousands of pizza prices from around the U.S., you see that you almost always get a much, much better deal when you buy a bigger pizza.