Fixture Unit Calculator
Calculate total fixture units (WSFU/DFU) for bathrooms, kitchens, and commercial spaces.
Results
Visualization
How It Works
Fixture units are a standardized way to measure water demand and drainage load. WSFU (water supply fixture units) determine pipe sizing for supply lines. DFU (drainage fixture units) determine drain pipe sizing.
The Formula
Total = Sum of (Fixture Count x Fixture Unit Value) for each type
Variables
- WSFU — Water Supply Fixture Units — measures supply demand
- DFU — Drainage Fixture Units — measures drainage load
Worked Example
A typical 2-bath home: 2 toilets (5.0 WSFU) + 2 lavs (2.0) + 1 tub (2.0) + 1 shower (2.0) + 1 kitchen (1.5) + 1 DW (1.5) + 1 washer (2.0) = 16.0 WSFU. Needs 1" supply.
Practical Tips
- Fixture unit values come from UPC/IPC plumbing code
- WSFU and DFU are different values for the same fixture
- Commercial fixtures have higher values than residential
- Peak demand is not the sum of all fixtures — diversity factor applies