🚿 Fixture Demand Calculator for Plumbing
Estimate simultaneous water demand from fixtures.
This free tool helps you turn project measurements into a practical planning estimate. Enter values in Vaelden’s interactive calculator, review the result, and confirm important assumptions against supplier data, measurements, codes or qualified advice before committing materials or money.
Open the Fixture Demand calculator →
How to calculate fixture demand
Method: Diversified demand = connected fixture flow × simultaneous-use factor
- Count fixtures served by the same supply.
- Use realistic fixture flow rates.
- Apply a justified simultaneity factor rather than assuming every fixture runs continuously.
Worked example
Using these planning inputs:
- Showers: 2
- Flow per shower: 9 L/min
- Taps: 2
- Flow per tap: 6 L/min
- Simultaneous use: 60 %
Estimated demand: 18.0 L/min
Reality check: Formal pipe sizing uses applicable loading units, pressure, velocity and code methods; this is only an early demand estimate.
Before you calculate
Use consistent units and the best measured inputs available. Real materials, equipment, site conditions and tolerances can change the result. Vaelden shows planning estimates; regulated, structural, electrical, plumbing, pressure and other safety-critical work still requires appropriate local compliance and professional advice.