Pipe Flow Calculator
Calculate flow rate and velocity for pipe and duct systems.
Results
Pipe flow rate depends on the cross-sectional area and fluid velocity. This calculator converts between pipe diameter, velocity and volumetric flow rate in multiple units. It is essential for plumbing, HVAC design, irrigation planning and industrial piping. Keep velocity between 1-3 m/s for water to balance friction losses and pipe cost.
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Frequently asked questions
Area = π × 0.025² = 0.001963 m². Flow rate = 0.001963 × 2 = 0.003927 m³/s = 235.6 L/min = 62.3 GPM.
100 GPM = 0.00631 m³/s. At 2 m/s, area needed = 0.00316 m². Diameter = √(4 × 0.00316/π) = 0.0634 m or 63.4 mm. Use a 3-inch (76.2 mm) pipe for some margin.
1.5-3 m/s for water mains, 0.5-1.5 m/s for domestic plumbing. Higher velocities cause noise and erosion. Lower velocities may allow sediment to settle.
1 GPM = 3.785 L/min. Multiply GPM by 3.785 for L/min or divide L/min by 3.785 for GPM. 100 GPM = 378.5 L/min.
Pipe material affects friction losses but not the Q = Av relationship. Smoother pipes (PVC, copper) have lower friction than rough ones (concrete, corrugated). This affects the pressure needed to maintain velocity.