Calculadora de Bomba d'Água
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
HP = Q·H·ρ / (3600·η·745,7); Q em m³/h
About this calculator
The Water Pump Calculator determines the power required for a hydraulic pump, in horsepower (HP) and watts (W), based on flow rate (Q, in m³/h), total head (H, in meters), fluid density (ρ, in kg/m³), and pump efficiency (η, as a decimal). The calculation uses the formula HP = Q × H × ρ / (3600 × η × 745.7), converting hydraulic power to the mechanical power needed at the pump shaft. This tool is useful for sizing pumps in water supply systems, irrigation, pools, and drainage.
To use the calculator, input the flow rate, head, density (default for water at 1000 kg/m³), and efficiency (typically between 0.5 and 0.9). The result shows power in HP and watts, along with theoretical hydraulic power. Note that total head includes geometric elevation, friction losses in pipes, and residual pressure required at the point of use.
Common use cases include: selecting a pump for a residential artesian well, sizing a pump to feed an elevated tank, or calculating power for a drip irrigation pump. The calculator prevents oversizing (which increases costs) or undersizing (which fails to meet demand).
Important cautions: actual pump efficiency varies with operating point; consult manufacturer curves for accuracy. Density of different fluids (e.g., saltwater or oil) must be adjusted. Losses in fittings, valves, and elbows should be included in total head. For complex systems, consult a hydraulic engineer.
Frequently asked questions
What is total head and how to calculate it?
Total head is the sum of geometric elevation, friction losses in pipes, and required pressure at the outlet. Measure the vertical height from source to highest point, add estimated losses (about 10-20% of pipe length), and the desired residual pressure.
What efficiency should I use in the calculator?
Typical efficiency for centrifugal pumps ranges from 0.5 to 0.85. Check the pump manual or use 0.7 as an initial average. Larger and newer pumps tend to have higher efficiency.
Can I use this calculator for submersible pumps?
Yes, as long as you input the correct total head, including the well depth. The formula is the same for submersible and surface pumps.
Does the calculator account for losses in bends and fittings?
Not directly. You must add these losses to the total head. Each bend, valve, or reducer adds a few meters of head loss; consult local loss tables.
What is the difference between hydraulic power and motor power?
Hydraulic power is the energy transferred to the fluid (Q × H × ρ / 3600). Motor power (HP) is higher due to internal pump losses (efficiency). The calculator provides both.