Short answer: A large pizza box is usually 16×16 inches (40×40 cm) because the pizza inside is 14 inches. Medium boxes are about 14×14; extra-large about 18×18.
| Pizza | Typical box (inches) | Box (cm) |
|---|---|---|
| Personal / 7–10 inch | 10×10 to 12×12 | 25–30 |
| Medium 12 inch | 14×14 | ~36 |
| Large 14 inch | 16×16 | ~40 |
| XL 16 inch | 18×18 | ~46 |
Corrugated height is usually 1.5–2 inches. If you are buying boxes, get the size above the pie, not equal to it. Slice counts: large pizza slices.