Fixture Units Calculator

Calculate total Water Supply Fixture Units (WSFU) and Drainage Fixture Units (DFU) for your project.

Tip: Enter the quantity of each fixture type. The calculator uses IPC Table 604.4 values.

Fixture Type	WSFU Each	DFU Each	Quantity	Total WSFU	Total DFU
TOTALS				0	0

About Fixture Units

Fixture units are a standardized way to measure the probable demand on a plumbing system. They account for the fact that not all fixtures operate simultaneously.

Water Supply Fixture Units (WSFU)

WSFU values represent the load that fixtures place on the water supply system. Higher values indicate greater water demand. Used for sizing water supply piping.

Drainage Fixture Units (DFU)

DFU values represent the load that fixtures place on the drainage system. Used for sizing drain, waste, and vent (DWV) piping.

Code Reference

IPC Table 604.4: Fixture unit values for common fixtures
IPC Table 604.5: Conversions from WSFU to GPM (Hunter's curve)
UPC Table 610.3: Equivalent UPC fixture unit values

Hunter's Curve (WSFU to GPM)

The conversion from fixture units to actual flow rate uses Hunter's curve, which accounts for the probability that multiple fixtures won't be used simultaneously.