Please don't do this here.

Omit internet tropes.

https://news.ycombinator.com/newsguidelines.html

No, even a standard 30-33cm pizza is barely enough for 1 person depending on hungry state.

A regular pizza of that size have about 2000 kcal of energy and an average male would need 2500 kcal a day (less for women), so unless you only have a single meal a day, which is unlikely, then it must be enough.

No, more in the 1000 kcal range.

Perhaps Costco pizzas - 18 inches, or about 45 cm!