Water Flow Calculator
Estimate GPM flow rate through your pipes
Nominal pipe size
Static pressure
Total length of pipe run
Affects friction coefficient
Flow Rate
—
GPM
Water Velocity
—
ft/s
Pressure Loss
—
psi
How to Use This Calculator
Our calculator uses the Hazen-Williams formula to estimate GPM flow rates through pipes.
- Identify pipe diameter and material
- Measure available water pressure
- Determine total pipe run length
- Enter specifications
AI Insights
Smart analysis for your project
Smart Estimates
Our AI cross-references material costs, regional pricing, and project complexity for more accurate estimates.
Waste Optimization
AI-calculated waste factors based on project type, not flat percentages. Saves 5-15% on material costs.
Best Practices
Recommendations derived from building codes, contractor data, and thousands of completed projects.
Calculation Formula
Hazen-Williams: Q = 0.442 x C x D^2.63 x (P/L)^0.54
Where C = roughness, D = diameter, P = pressure, L = length
Frequently Asked Questions
What is a good water flow rate for a house?
A residential system should deliver 6-12 GPM at fixtures. Minimum acceptable is 4 GPM.
What is max water velocity in pipes?
Max recommended velocity is 8 ft/s for copper and 12 ft/s for PVC. Excessive velocity causes erosion and noise.