your all wrong.....
it's: Pi*(d^2)/4
I'm Joking... ok....
to get the volume of a cylinder:
Pi*(d^2)/4*h
to get the surface area of same cylinder
( (2*(Pi*(d^2)/4)) + (Pi*d*h) )
where:
h = height of cylinder
Pi = Pi or you favorite numeral to the approximate equivalent thereof
d= diameter of cylinder
opperand significance: ^*/+- in that order
why only I work with diameter, and not radius...
well simple... try to measure the Radius of a round object, using a micrometer....