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Pipes - Fluid Flow Velocities

Calculate fluid velocity and volume flow in pipes and tubes.

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Imperial units

Fluid flow velocity in a circular pipe can be calculated with Imperial or American units as

v = 1.273 q / d2

= 0.4084 qgpm / din2                               (1)


v = velocity (ft/min, ft/s)

q = volume flow (ft3/s, ft3/min)

d = pipe inside diameter (ft)

qgpm = volume flow (US gal/min, gpm)

din = pipe inside diameter (inches)

Online Pipe Velocity Calculator - Imperial Units

volume flow (US gal/min, gpm)

pipe inside diameter (in)

Dimensions: Steel Pipes schedule 40 & 80, PVC and CPVC Pipes Schedule 40 & 80, Copper Tubes and PEX Tubes

volume flow (ft3/s, ft3/min)

pipe inside diameter (ft)

Flow velocities in steel pipe schedule 40

SI units

Fluid flow velocity in a circular pipe can be calculated with SI units as

v = 1.273 q / d2                            (2)


v = velocity (m/s)

q = volume flow (m3/s)

d = pipe inside diameter (m)

Online Pipe Velocity Calculator - SI Units

volume flow (m3/s)

pipe inside diameter (m)

Example - Flow Velocity in a Steel Pipe

60 US gal/min is flowing through a 4 inch schedule 80 steel pipe. The internal diameter of the pipe is 3.83 in. The velocity can be calculated as

v = 0.4085 (60 gal/min) / (3.83 in)2   

   = 1.7 ft/s

Flow velocities in steel pipe schedule 40 metric units

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