Have you ever wondered if you'd get more pizza when buying a 15" 'no crust' versus a 12" buy-one-get-one-free deal?
If so, this is the web page for you. Adopting the famous πr2 equation for determining the area of a circle, this web page calculates how much each cm2 of pizza will cost you, and highlights the best value.
The diameter and crust size can be any units you like (usually inches), provided they are consistent, and the cost can be in any units, also. (Penny is just used to imply there's 100 of them in your currency unit.)
So, enter the details from the menu of your local pizzeria, and work out the best deals!
p.s. remember to hit return after changing the numbers, so the calculations can be run again.