Method: Hydraulic power for water is calculated from: P_hyd = ρ × g × Q × H where Q is flow rate, H is total dynamic head, ρ is water density and g is gravitational acceleration. Pump efficiency is: η_pump = hydraulic power ÷ shaft power × 100 If electrical input power is selected: shaft power = electrical input power × motor efficiency and: wire-to-water efficiency = hydraulic power ÷ electrical input power × 100 This calculator assumes water density of approximately 1000 kg/m³. Actual pump efficiency should be evaluated at the measured operating flow and head and compared with the manufacturer’s performance curve.