Why are pizza boxes square?

Pizza boxes are square because square boxes are easy to assemble and the strong corners are resistant to crushing. Before square corrugated cardboard boxes, pizza was placed on cardboard circles and then in paper bags, which was inconvenient for both delivery and takeout.

The modern pizza box was developed in 1977 and replaced the paper bag method as well as an alternative clayboard box design. The square boxes, made of corrugated cardboard, shipped flat and were assembled at the pizza restaurant. The new design kept pizza warmer, enabled stacking and helped make delivery a common business practice in the pizza industry.