Many pizza places offer special “deals” if you order two medium pies. You might think that two mediums deliver more cheesy goodness than one large pie, but usually you’d be mistaken. From Primer, a mathematical comparison of two 12″ pizzas and one 18″ pizza:
Area of two 12” pizzas:
12/2 = 6 6×6=36 36xπ = 113.1 in² x 2 = 226.2 in²
Area of one 18” pizza:
18/2=9 9×9=81 81xπ = 254.5 in²
And as we know, more pizza is always better.
(via Cliff Pickover)
Source: Why you should almost always order one large pizza instead of two mediums