Fixture Unit Demand Calculator (Supply Sizing)

Supply piping is sized on demand - but the demand that matters is the probable peak, not the sum of every open tap. Fixture units convert a fixture schedule into one comparable number, and a demand curve turns that number into flow.

Fixture Unit Demand Calculator builds the WSFU total and converts it to peak flow and a suggested supply size for preliminary domestic-water pipe design.

• Fixture library: Toilets, sinks, showers, machines, hose bibs.
• WSFU totals: Sums with per-fixture accounting.
• Hunter curve: WSFU to probable peak GPM.
• Supply size: Suggested pipe at working velocity.
• Live update: Results while you type.
• Export: Text, CSV or JSON report.

1. Count your fixtures in each input.
2. Choose supply or private values if offered.
3. Read the WSFU total and probable peak flow.
4. Note the suggested supply size.
5. Export the schedule if needed.

Example 1. A 3-bath house - 3 toilets, 3 lavatories, 3 showers, 1 kitchen sink, 1 washer, 1 dishwasher - sums to roughly 25 WSFU and suggests around 18-20 GPM peak demand.

Example 2. A small office with 4 toilets, 4 lavatories, 2 sinks and a coffee sink lands lower - near 10 WSFU and about 8 GPM.

• One comparable number: WSFU unifies a fixture list.
• Honest peak: Probable demand, not worst-case.
• Quick pipe size: Suggested supply bore fast.
• Field ready: No chart hunting.
• Free and private: No uploads, no logging.