Pump Power Calculator
Find hydraulic power a pump must deliver.
Vertical height plus friction losses the pump overcomes.
Water is about 1000 kg/m³.
Results update as you type.
How it works
Pump power is the rate at which a pump must add energy to a fluid to move it at a given flow and lift, and this pump power calculator finds the hydraulic power in watts from the flow rate, the head, the fluid density, and gravity. Head captures both the vertical height the fluid rises and the friction it must overcome, so the result is the useful power the pump imparts to the fluid stream. This matters when selecting and sizing pumps: water supply, irrigation, drainage, heating circuits, and industrial process lines all need a pump matched to the required flow and head. Undersizing starves the system while oversizing wastes energy and money. A pump power calculator gives the hydraulic power baseline, which you then divide by the pump and motor efficiency to find the actual electrical power the pump will draw. The formula works because density times gravity times head is the pressure the pump must generate, and pressure times volumetric flow rate equals power. Physically, the pump lifts a certain mass of fluid each second through the head, and this is the rate of work that requires. Mechanical, civil, and building-services engineers, along with technicians, use a pump power calculator to specify pumps and estimate running energy costs.
P = density × gravity × flow rate × head
The hydraulic power a pump delivers to a fluid equals the fluid density times gravitational acceleration times the volumetric flow rate times the head. Density times gravity times head gives the pressure the pump must add, and multiplying that pressure by the volume flow rate gives power. In effect the pump raises a given mass of fluid per second through the head height, and this term is the rate of work needed to do so.
Source:Standard fluid mechanics (hydraulic power P = ρgQH)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter flow rate, head, fluid density and gravity.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Hydraulic power updates instantly as you type — no button to press.
Frequently asked questions
How is pump power calculated?
Hydraulic pump power equals the fluid density multiplied by gravitational acceleration, the volumetric flow rate, and the head. For water at 1000 kilograms per cubic metre pumping 0.05 cubic metres per second against 10 metres of head, the power is 1000 times 9.81 times 0.05 times 10, or 4905 watts. This is the useful power added to the fluid, before accounting for pump inefficiency.
What is pump head?
Head is the total energy per unit weight the pump must add to the fluid, expressed as an equivalent height in metres. It combines the static lift, the vertical distance the fluid rises, with friction losses in the pipes and fittings and any pressure difference to overcome. A higher head means the pump works harder for the same flow, so accurate head figures are essential for correct sizing.
Is this the electrical power the pump uses?
No. This calculates the hydraulic power delivered to the fluid, which is the useful output. The electrical power the pump draws is larger, because pumps and motors are not perfectly efficient. Divide the hydraulic power by the combined pump and motor efficiency, often between 0.5 and 0.8, to estimate the actual input power. That input figure is what determines running costs and the required supply.
Why do density and gravity appear in the formula?
Density and gravity convert the head, a height, into the pressure the pump must produce, since pressure from a column of fluid equals density times gravity times height. Denser fluids need more power to pump to the same head because each cubic metre weighs more. Water is about 1000 kilograms per cubic metre; oils and slurries differ, so enter the correct density for accurate results.
How do I convert the result to horsepower?
The calculator gives hydraulic power in watts. To convert to mechanical horsepower, divide by about 745.7, so 4905 watts is roughly 6.6 horsepower of hydraulic output. Remember this is the fluid power, not the motor rating; the motor must be larger to cover losses. Divide by efficiency first, then convert, to estimate the horsepower the driving motor actually needs.