# Power Number

Power number, abbreviated as \(N_p\), is a dimensionless number that represents the proportional drag force and inertial force. It is used in momentum transfer and power consumption by fans, mixers and pump impellers at a specified rotational speed. The calculation and formula for the Power Number are shown below. Note: it may be referenced as the Newton Number.

\(\large{ N_p = \frac {P}{\rho \; n^3 \; d^5} }\) Where: \(\large{ N_p }\) = Power number \(\large{ \rho }\) (Greek symbol rho) = density of the fluid \(\large{ d }\) = diameter of stirrer \(\large{ P }\) = power \(\large{ n }\) = rotational speed |

Tags: Equations for Power