What This Calculator Does
This tool calculates the total holding capacity of a cylindrical tank — common for water storage, propane, fuel, and septic tanks — from its diameter and height (or length, if the tank lies on its side).
The Formula
Tank volume is based on the geometry of a cylinder: Volume = π × radius² × height. Since a cylinder’s total volume doesn’t depend on whether it stands upright or lies on its side, the same formula applies to both orientations. The result in cubic feet is then converted to US gallons (× 7.48052) and liters (× 28.3168).
This calculates the tank’s full, total capacity. For a partially filled horizontal tank, actual liquid volume at a given fill level is smaller and requires a separate partial-volume (circular segment) calculation. Always verify against the manufacturer’s rated capacity for critical applications.