Fixture Unit Calculator

Add up drainage (DFU) and water-supply (WSFU) fixture units from your fixture counts to size drains and supply piping. Build a fixture list and the calculator totals both, plus a minimum building-drain size.

Fixtures

Fixture Units

Total Drainage (DFU)4
Total Supply (WSFU)3.5
Min Building Drain2"

DFU/WSFU values are typical private-use figures; drain size from IPC Table 710.1(2) at 1/4"/ft. Verify against the governing plumbing code (IPC/UPC).

Fixture-unit values shown are typical private-use figures; the minimum drain size uses IPC Table 710.1(2) at 1/4" per foot. Values differ between IPC and UPC and by fixture type — verify against the governing code.

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