What it calculates
Estimate combined fixture flow in gallons per minute.
Fixture Flow Calculator
Estimate combined flow for active plumbing fixtures.
Planning and estimating aid only. Verify project requirements, manufacturer instructions, adopted codes, permits, and field conditions before performing regulated work.
Plumbing planning
How to Use This Calculator
Use the field units shown below, then compare your result with the worked example. Count only the simultaneous scenario you intend to analyze.
How the calculation works
Each active fixture count is multiplied by its entered GPM and the flows are added together.
What the result means
This estimates simultaneous flow, not fixture units or code-required pipe sizing.
Add a stated simultaneous-flow scenario
Two showers at 2 GPM each plus one faucet at 1.5 GPM give 2 × 2 + 1 × 1.5 = 5.5 GPM. This scenario assumes those fixtures are operating at the same time at the entered flow rates.
Contractor tip: Count only the simultaneous scenario you intend to analyze. Compare different scenarios without presenting their sum as a verified peak demand for the building.
Verify the final quantity
This is a direct sum, not a fixture-unit demand method or a pipe-sizing calculation. Actual fixture flow depends on product characteristics and available pressure. Other demand must be added explicitly.
Good practice: Compare the calculated quantity with plans, specifications, product packaging and current field conditions before purchasing material.