In order to answer why pizza slices are triangles, we first must ask “Why are pizzas round?”
It all starts with creating the dough. Ingredients are kneaded together into a ball and then left to rise. Why a ball? Because it's easier to make than any other shape. Imagine having to form every piece of dough into perfect squares or octagons!
It's also much easier to stretch dough into a circle. A dough ball is stretched with a rolling pin, starting from the center outwards. Sometimes pizza dough is stretched by tossing it into the air and spinning it. The centrifugal force (centrifugal means moving away from the center) causes it to expand into a circular shape. This shape is best for baking. It allows a pizza to be evenly cooked.
When the pizza is done baking, it's time to cut! If pizzas are round, then why are pizza slices triangles? The circular shape makes it easy to slice into equal pieces. The most common way to equally divide a circle is to cut it into triangular pieces, just like a pie chart. By slicing it from the outer crust to the center, every slice gets an equal portion of toppings and crust!
Pizza has been around for centuries, but circular pizzas became standard in 1984. The Associazione Verace Pizza Napoletana (True Neapolitan Pizza Association) declared that pizza should be round and not more than 13.7 inches in diameter. But this doesn't stop people from making square, rectangular and even heart-shaped pizzas. What shape of pizza would you like to try?