Estimate water flow rate through a pipe using the Hazen-Williams equation, based on pipe diameter, length, pressure, and material.
How to Use the Pipe Flow Rate Calculator
Enter the pipe "Diameter (mm)" and "Length (m)" for the pipe run you want to estimate.
Enter the available "Water Pressure (bar)" and select the "Pipe Material" from the dropdown.
Click "Calculate" to see the estimated flow rate in L/min and US GPM.
Frequently Asked Questions
It uses the Hazen-Williams equation, a widely used method for estimating water flow through pipes based on diameter, length, pressure (head loss), and a roughness coefficient (C-factor) for the pipe material.
The C-factor represents pipe roughness — smoother pipes (like PVC/CPVC, C≈150) allow higher flow for the same pressure than rougher ones (like old cast iron, C≈100). Choosing the correct material gives a more accurate estimate.
No — it's a close engineering estimate. Actual flow can vary due to fittings, bends, valves, pipe age/corrosion, and elevation changes not accounted for here.
Yes, it's completely free and requires no sign-up.