Tank Volume Calculator
Calculate the volume in gallons of a cylindrical or rectangular water tank, cistern or vessel from its dimensions.
About the Tank Volume Calculator
This calculator finds the volume held by a cylindrical or rectangular tank, cistern or vessel, in both cubic inches and US gallons, from its dimensions and either its full height or current fill level.
Formula: Cylindrical: Volume = π × Radius² × Height; Rectangular: Volume = Length × Width × Height; Gallons = Cubic Inches ÷ 231 (one US gallon equals 231 cubic inches)
Use the fill level instead of the tank's full height to check how much liquid is currently stored rather than total capacity. For horizontal cylindrical tanks partially filled, this simple formula won't apply — that requires a more complex partial-cylinder calculation.