Pipe Size Calculator
Find the right water supply pipe size for your project
Sum of WSFU
Static pressure at meter
From meter to farthest fixture
Main Supply Line
—
inches
Branch Lines
—
inches
Peak Flow Rate
—
GPM
Disclaimer: Results are estimates based on standard formulas. Not a substitute for professional advice from a licensed contractor, engineer, or architect. Verify all calculations before making purchasing or construction decisions.
How to Use This Calculator
Our pipe size calculator follows UPC and IPC guidelines to recommend the right pipe diameter.
- Add up WSFU for all fixtures
- Measure static pressure at meter
- Determine longest pipe run
- Enter specifications
- Consider future additions
Expert Insights
Smart analysis for your Plumbing project
PEX vs Copper Analysis
PEX: 40-60% less labor, freeze-resistant. Copper: longer lifespan, antimicrobial. AI compares total installed cost for your project scope.
Fixture Unit Sizing
AI calculates total water supply fixture units (WSFU) per UPC/IPC code to size your main and branch lines correctly.
Pressure Regulation Check
Street pressure over 80 PSI requires a PRV. AI flags high-pressure scenarios and recommends the right valve size.
Calculation Formula
Based on UPC/IPC tables:
Flow rate from WSFU conversion
Pipe size from flow rate x pressure x length
Authority References
Our calculations are based on guidelines and standards from these authoritative sources:
- International Association of Plumbing and Mechanical Officials (IAPMO) — Uniform Plumbing Code (UPC). Learn more
- International Code Council (ICC) — International Plumbing Code (IPC). Learn more
Frequently Asked Questions
What size pipe for a main water line?
Most homes use 3/4" or 1" copper/PEX for main supply. Size depends on fixtures and pressure.
What are WSFU?
Water Supply Fixture Units: bathroom faucet = 1, shower = 2, toilet = 2.5, kitchen sink = 1.5, washing machine = 4.