What this calculator does
The pipe volume calculator finds how much liquid or gas a pipe, tube, or cylindrical vessel can hold internally, based on its inside diameter and length.
The formula
The volume of a cylinder is V = π × r² × L, where r is the inside radius and L is the length. This calculator takes the inside diameter, halves it to get the radius, and multiplies by the length (converted to consistent units) to get the volume in cubic inches, then converts that to US gallons (1 gallon = 231 in³), liters, and cubic feet for convenience.
- Always use the pipe’s inside diameter (ID), not its outside diameter (OD), since wall thickness reduces the usable interior space.
- This calculates the geometric internal volume only; it does not account for fittings, valves, or partial fill levels.
This tool is for general planning and educational purposes in plumbing and construction work.
Last reviewed August 2026