Construction Calculator - Water and Utility

Pipe Volume Calculator

Calculate water volume inside a pipe from diameter and length.

Reviewed: August 26, 2026

Calculate Pipe Volume

For the Pipe Volume Calculator, enter inside diameter and pipe length. It models the pipe interior as a cylinder and reports cubic feet and U.S. gallons from inside diameter and length.

Construction measuring tools arranged beside a residential building project

Formula used

Full pipe volume = π × (inside diameter ÷ 2)² × length; U.S. gallons = cubic feet × 7.48052

Pipe Volume Calculator measurement plan showing Inside diameter inches, Pipe length feet

Worked pipe volume example

Pipe Volume Calculator example: π × (5.4 in ÷ 12 ÷ 2)² × 134.5 ft = 21.39 ft³. A completely full pipe therefore holds approximately 160.02 U.S. gallons.

Interpret gallons and flow

Read gallons for operating volume and cubic feet for geometry, adding connected equipment volumes separately when needed.

System effects the formula omits

Fittings, valves, reducers, elevation changes, trapped air, wall thickness tables, and partial fill are outside a straight full-bore cylinder.

Questions specific to this calculation

Should I enter inside or outside pipe diameter?

Use the pipe's inside diameter—not nominal size or outside diameter—and the actual filled length.