Fluid Flow

Blower & Fan Calculation

Blower & Fan generate pressure to move Air (or Gases) for ventilation and industrial process requirements. This web application calculate power required for air flow and also determine performance for different fan speed and diameter based on Affinity Laws.

Operating Data

inch H2O

Efficiency, η



In English units, Fan Power is calculated as following :

\displaystyle \displaystyle Fan Power (hp) = \left(\frac{Air Flow * Static Pressure}{6356*\eta}\right)

\displaystyle \displaystyle \eta = \eta_{Fan}*\eta_{Belt}*\eta_{Motor}*\eta_{Drive}


  • Air Flow in cubic feet per minute
  • Static Pressure in inches of water column


Fan Laws

Air Flow, Q varies as following, where 1 denotes Existing details, 2 denotes New details, D is Fan Diameter and N is Fan Speed.

\displaystyle \displaystyle Q_{2} = Q_{1}\left(\frac{D_{2}}{D_{1}}\right)^{3}\left(\frac{N_{2}}{N_{1}}\right)

Static Pressure, SP varies as following :

\displaystyle \displaystyle SP_{2} = SP_{1}\left(\frac{D_{2}}{D_{1}}\right)^{2}\left(\frac{N_{2}}{N_{1}}\right)^{2}

Power varies as following :

\displaystyle \displaystyle Power_{2} = Power_{1}\left(\frac{D_{2}}{D_{1}}\right)^{5}\left(\frac{N_{2}}{N_{1}}\right)^{3}