question for a math wiz?

[e-paw]

I was working on a diesel fueling platform today, eyeballing up the size of the storage tanks to look right for the project. I felt that 2 tanks for #2 oil were needed and 1 for lube oil would work out fine. I cut up some heavy card board cylinders to size, they will be covered by a styrene wrapper with rivet detail on it. Then I wondered what the capacities of the tanks were? I racked my brain for a while trying to remember some 5th grade geometry, it seams that my old age (35 ) has to crept up on me when I wasn't looking. I just can't remember how to find the square footage of a cylinder and convert it to gallons. Please help..... the measurements are : diesel fuel- 29 feet in diameter x 13 feet high
lube oil- 13 feet in diameter x 11 feet high

Thanks