PlumbMath

Calculation aids for working plumbers. Every tool shows its math and cites the code sections and documents it is built on.

Tools

• Gas pipe sizing calculator. Low pressure natural gas, Schedule 40 steel pipe or copper tubing, longest length or branch length method, from the 2024 IFGC equations.
• Drainage fixture unit calculator. Fixture units and the minimum size of horizontal branches, stacks, the building drain and a building sewer up to 6 in., under the 2024 IPC or the 2024 UPC.
• Rolling offset calculator. Travel, run, roll angle and cut length between two parallel pipes with two fittings of any angle, with catalog take-outs for copper and PVC elbows.
• Pipe volume calculator. Gallons and litres of water in a run of copper, steel, PVC or PEX by nominal size and length, with the weight of that water.
• Tankless water heater sizing calculator. Flow, temperature rise and the heat input a tankless heater needs for the fixtures that run at the same time, from the heat equation and federal test constants.

Reference

• Plumbing and fuel gas codes by state. Which plumbing code and which fuel gas code each state and the District of Columbia adopts, with edition, effective date, state amendments and scope, each filled row checked against an official source.

How the tools are built

• Numbers come from the published codes and documents, with section numbers and links on the methodology page.
• The tools run in your browser. Nothing you enter is sent anywhere.
• A result is a calculation aid. The code adopted where you work and your code official govern.