IPC Table 604

Pipe Sizing Calculator

Enter your fixture counts and longest pipe run to get the correct supply line diameter per IPC Table 604.3 / 604.4. Used by licensed plumbers for rough-in sizing.

Fixture counts

Toilets (tank type) (3 FU each) Bathroom lavatory sinks (1 FU each) Tubs / showers (2 FU each) Kitchen sinks (2 FU each) Dishwashers (1.5 FU each) Washing machines (4 FU each) Hose bibbs (outdoor) (2.5 FU each) Other fixtures (each) (1 FU each)

Longest pipe run (feet) Pipe material

Minimum 40 PSI at fixtures (recommended)

How IPC pipe sizing works

Fixture units (FU). The International Plumbing Code assigns each fixture a demand load in "fixture units." A toilet draws 3 FU, a washing machine 4 FU, a kitchen sink 2 FU. Fixture units model simultaneous demand probability — not raw flow rate.
Run length adjustment. Longer pipe runs have higher friction losses, so the same fixture unit load requires larger pipe. IPC Table 604.4 provides three columns: runs ≤40 ft, ≤80 ft, and ≤160 ft. Enter your longest run from the meter to the farthest fixture.
Material note. Copper, PEX, and CPVC have similar inside diameters at standard sizes, so the code sizing is equivalent across materials. The calculator notes the common trade name (Type L copper, PEX-A/B, CPVC SCH 40) but the nominal size is the same.
Branch sizes. Per IPC Section 604.5, individual fixture branches are sized separately — most single fixtures require ½" minimum; washing machines require ¾". The calculator outputs branch recommendations alongside the main line size.

When to consult a licensed plumber

This calculator uses IPC Table 604 directly and is appropriate for standard residential rough-in planning. Commercial buildings, fire-sprinkler integration, booster pump systems, or any jurisdiction using UPC (Uniform Plumbing Code) instead of IPC requires a licensed plumber's sealed drawings. Most jurisdictions require a permit and inspection for any supply-line rough-in.

Code references: methodology page.