Pump power formula
Hydraulic power is the useful work done on the liquid: P = ρ g Q H. Shaft power is higher because the pump is not 100% efficient. Sea-water density is about 1025 kg/m³. Fresh water is 1000 kg/m³. Efficiency for a ship’s centrifugal pump is often 60–75% at the duty point.
How this calculator works
Q is converted from m³/h to m³/s. Hydraulic kW = ρ × 9.81 × Q × H ÷ 1000. Shaft kW = Hydraulic kW ÷ (η/100). Motor current also depends on voltage and power factor, so this is not an electrical load calculation. Check the pump curve for the real duty point.
Who should use it
Useful for engineers sizing a pump or checking why a motor is overloaded. Use the nameplate and the maker’s curve for the official figure.