Pipe Size Calculator
Determine the correct pipe size for flow requirements.
How It Works
Flow (ft³/s) = GPM × 0.002228. Area = Flow ÷ Velocity. Diameter = 2 × sqrt(Area × 144 ÷ π).
Example
12 GPM at 5 ft/s needs ≈1 in pipe.
Frequently Asked Questions
What is a good water velocity?
5 ft/s is a common design target; higher speeds cause noise and erosion.
Why convert GPM to ft³/s?
The area/velocity formula works in consistent units, so gallons per minute is converted to cubic feet per second.
Does material affect sizing?
Not in this simplified calculator — pipe roughness matters for long runs, but size here is driven by flow and velocity.