Pipe Volume Calculator

About this calculator

The liquid a pipe can hold is a straight cylinder volume problem: V = π × r² × L, where r is the pipe’s inner radius (half the inner diameter, not the outer or nominal pipe size) and L is its length. Because pipe walls have thickness, the inner diameter is always a bit smaller than the labeled nominal size, so using the true bore is what makes the result accurate.

Plumbers, irrigation designers and process engineers use this figure to size holding volumes, estimate purge or flush volumes before a chemical changeover, calculate fluid weight for structural supports, or work out how much water is trapped in a run of pipe during draining or dosing. This calculator converts the resulting volume into liters, US gallons and cubic meters so it is usable across trades and regions.