Irrigation Pipe Size Calculator
Estimate minimum irrigation-pipe inside diameter from flow and target velocity, plus line volume, fill time and pipe cost allowance.
Default project preview
1.28 in
Required flow area
1.28 in²
Line water volume
10 gal
Line fill time
0.5 min
Pipe length
150 ft
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Required flow area = volumetric flow ÷ target velocity. Inside diameter = √(4 × flow area ÷ π). Line volume uses that calculated area and entered length.
FAQ
Irrigation Pipe Size Calculator questions
Why use actual inside diameter?+
Nominal pipe sizes can have different inside diameters depending on material and wall thickness.
Does a larger pipe reduce pressure loss?+
Generally yes, because velocity and friction loss decrease for the same flow.
Does this calculator include fittings?+
No. Valves, elbows, filters and elevation add pressure requirements that need a full hydraulic check.