The formula to calculate Impeller Diameter (D) is:

\[ D = \sqrt{\frac{2.35 \cdot 108 \cdot Ps}{\psi \cdot N^2}} \]

Where:

• \(D\) is the diameter of the impeller (in.).
• \(Ps\) is the pressure requirement (in. H2O).
• \(\psi\) is the pressure coefficient (0.05 to 2.0).
• \(N\) is the speed of the impeller (rpm).