How do I calculate the right pipe diameter?

Enter your flow rate (GPM) and pipe run; the calculator returns the recommended diameter and friction loss instantly.

What pipe size do I need for a given GPM?

It depends on flow and length - enter both and PlumbCalc Pro gives the correct size.

Yes, the calculator is free to use in your browser.

The pipe and gas sizing cheat sheet we keep on the phone — the numbers, and the three that fail inspection most often.

Free in the browser. No signup to run one.

Visual Pipe ID — Identify a pipe size from a photo when the stamp is painted over or gone.
Pipe Sizing — Diameter from flow rate and allowable pressure drop.
DWV Drain Sizing — Drainage fixture units to minimum branch, stack and building drain size (IPC 709.1 / 710.1).
Vent Sizing — Minimum vent size and its developed-length limit, plus the half-the-drain-diameter floor (IPC 916.1).
Gas Pipe Sizing — Gas line diameter by load and run length (NFPA 54).
Offset Calculator — Travel, run and fitting angles for a rolling or simple offset.
Flow Rate — GPM and velocity for a given diameter.
Material Estimator — Quantity takeoff by job type.
Material Markup — Cost plus labor plus overhead to a sell price.
Labor Estimator — Hours and cost by job type.
Permit Fees — Permit cost by jurisdiction and job value.
Good-Better-Best — Tiered pricing presentation for higher close rates.