Construction Calculators

Pipe Volume Calculator

Calculate the volume of water or fluid held inside a length of pipe from its inside diameter and length.

Volume —

About the Pipe Volume Calculator

This calculator finds how much water or fluid is held inside a run of pipe, based on its inside diameter and length — useful for sizing expansion tanks, estimating drain-down volume or dosing chemicals into a closed loop.

Formula: Volume = π × Radius² × Length (converted to inches); Gallons = Cubic Inches ÷ 231

Always use the pipe's actual inside diameter, not its nominal size — schedule 40 PVC and copper pipe both have wall thickness that reduces the true bore diameter below the labeled size.