Fixture units per fixture (WSFU & DFU)

Plumbing codes size supply pipes and drains not by the number of fixtures but by their fixture units — a weighting for how much each fixture demands (WSFU on the supply side) or discharges (DFU on the drain side). The values below are labeled IPC/UPC planning conventions, not a code citation — your local plumbing code governs. Use them in the water-supply fixture units and drainage fixture units tools.

FixtureWSFU (supply)DFU (drain)
Water closet (toilet)2.23
Lavatory (bathroom sink)0.71
Bathtub / tub-shower1.42
Shower stall1.42
Kitchen sink1.42
Clothes washer / laundry1.42
Floor drain—2
Hose bibb (outdoor faucet)2.5—

Labeled IPC/UPC planning conventions — WSFU (water-supply fixture units) size the supply, DFU (drainage fixture units) size the drain and vent. Your local plumbing code sets the values it uses.

Related calculators

Drainage Fixture UnitsAdd up the drainage fixture units (DFU) for your toilets, sinks, tubs, showers and laundry to size the drain and vent with the standard IPC/UPC method.Water Supply Fixture UnitsAdd up the water-supply fixture units (WSFU) for your home from a simple fixture count, then feed the total into peak-demand and supply-pipe sizing.