From Superfan, India’s first super energy efficient ceiling fan

Formulae 1 to 4 can be applied to any fan provided the diameter does not change. If the diameter does not change the fans must be geometrically similar. The units of density, fan rotational speed and diameter are not important as long as both are the same.

In formulae 5 to 8 the units shown in the nomenclature must be used to satisfy the formulae

Volume Flow


Absorbed Power

Sound Power Level


Fan Total Efficiency %

Fan Total Pressure

Fan Static Pressure

Velocity Pressure

Nomenclature for symbols used in this page:


[1] F. P. Bleier, Fan Handbook: Selection Application and Design, New York, NY, USA:McGraw-Hill, 1997.

[2] M.J. McPherson, Subsurface Ventilation and Environmental Engineering, Chapter 10

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