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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 q gpm / d in 2(1)


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

q = volume flow (ft 3 /s, ft 3 /min )

d = pipe inside diameter (ft)

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

d in = pipe inside diameter (inches)

Online Pipe Velocity Calculator - Imperial Units

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

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 (m 3 /s)

d = pipe inside diameter (m)

Online Pipe Velocity Calculator - SI Units

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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