Hello: Please advise how to use the formula I saw for determining the number of gallons in a cylinder? This is how it was written

V = pi r² h

. does this mean pie, or 3.14 X radius squared, X the height? If so please use a standard 55 gal barrel (1' R & 3' H) for example?

Thanks, Jim

Hi Jim,

You are correct about pi, it is approximately 3.1416. If the barrel has a one foot radius (r = 1) and a three foot height (h = 3) then the volume is

V = pi r² h = 3.1416 1² 3 = 9.4248 cubic feet

One cubic foot is 7.48 gallons(US) so 9.43 cubic feet is

9.43 7.48 = 70.49 gallons

I would measure your barrel again. I measured one I have and the diameter was approximately 22 inches so the radius is 11 inches which is 0.91667 feet. I also got a height of 33 inches or 2.75 feet. Thus I get, for a volume

V = pi r² h = 3.1416(0.91667)² 2.75 = 7.26 cubic feet
7.26 7.48 = 54.3 gallons

Penny

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