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
Sound Power Level
Fan Total Efﬁciency %
Fan Total Pressure
Fan Static Pressure
Nomenclature for symbols used in this page:
 F. P. Bleier, Fan Handbook: Selection Application and Design, New York, NY, USA:McGraw-Hill, 1997.
 M.J. McPherson, Subsurface Ventilation and Environmental Engineering, Chapter 10