Pumps - Power Calculator

Calculate pumps hydraulic and shaft power.

Hydraulic Pump Power

The ideal hydraulic power to drive a pump depends on

the mass flow rate the
liquid density
the differential height

Pump power - si imperial units

- either it is the static lift from one height to an other or the total head loss component of the system - and can be calculated like

P_h(kW) = q ρ g h / (3.6 10⁶)

= q p / (3.6 10⁶) (1)

where

P_h(kW) = hydraulic power (kW)

q = flow (m³/h)

ρ = density of fluid (kg/m³)

g = acceleration of gravity (9.81 m/s²)

h = differential head (m)

p = differential pressure (N/m², Pa)

The hydraulic Horse Power can be calculated as:

P_h(hp) = P_h(kW) / 0.746 (2)

where

P_h(hp) = hydraulic horsepower (hp)

Or - alternatively

P_h(hp) = q_gpm h_ft SG / (3960 η) (2b)

where

q_gpm = flow (gpm)

h_ft = differential head (ft)

SG = Specific Gravity (1 for water)

η = pump efficiency

Example - Power pumping Water, SI Units

1 m³/h of water is pumped a head of 10 m. The theoretical pump power can be calculated as

P_h(kW) = (1 m³/h) (1000 kg/m³) (9.81 m/s²) (10 m) / (3.6 10⁶)

= 0.027 kW

Example - Power pumping Water, Imperial Units

600 gpm of water is pumped a head of 110 ft. The efficiency ofthe pump i s 60% (0.6) and the specific gravity of water is 1. The pump shaft power can be calculated as

P_h(kW) = (60 gpm) (110 ft) (1) / ((3960) (0.6))

= 27.8 hp

Shaft Pump Power

The shaft power - the power required transferred from the motor to the shaft of the pump - depends on the efficiency of the pump and can be calculated as