# Pipes and Fluid Flow Velocities

## Calculate fluid flow and pipe velocities in pipes and tubes

### Imperial units

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

v = 1.273 q / d^{2 }

= 0.4084 q_{gpm}/ d_{in}^{2}(1)

where

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

*volume flow ( ft^{3}/s, ft^{3}/min)*

*pipe inside diameter (ft)*

*volume flow (US gal/min, gpm)*

*pipe inside diameter (in)*

### SI units

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

v = 1.273 q / d^{2}(2)

where

v = velocity (m/s)

q = volume flow (m^{3}/s)

d = pipe inside diameter (m)

#### Online Pipe Velocity Calculator - SI Units

*volume flow (m ^{3}/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*