Horsepower Required to Pump Water

Calculate the water horsepower required to pump water using flow rate and head, or delivered pressure. Includes both imperial and metric unit calculations.

Horsepower Required to Pump Water

Energy imparted to water by the pump is called water horsepower and can be calculated using two methods:

Method 1 - Using Flow and Head:

Pwhp = q h SG / (3960 μ)
q = flow (gal/min)
h = head (ft)
SG = specific gravity (1 for water)
μ = pump efficiency (decimal)

Method 2 - Using Delivered Pressure:

Pwhp = q dp / (1715 μ)
dp = delivered pressure (psi)

Metric Units:

P = q h ρ / (6116×10³ μ)
q = flow (liter/min)
h = head (m)
ρ = density (kg/m³)

Calculator

Inputs

Calculation Method

Flow Rate (gal/min) (gal/min)

Head (ft) (ft)

Specific Gravity (dimensionless)

Pump Efficiency (decimal (0-1))

Delivered Pressure (psi) (psi)

Flow Rate (liter/min) (liter/min)

Head (m) (m)

Density (kg/m³) (kg/m³)

Pump Efficiency (decimal (0-1))

Results

Water Horsepower-- hp

Power Required-- kW