Physics

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Physics

Centrifugal Pump Power Calculator.

Calculates the hydraulic power required to pump a fluid based on flow rate, head, and fluid density.

Results update live as you type.
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Your inputs

How it works

  1. 1

    Convert flow rate from m³/h to m³/s by dividing by 3600.

  2. 2

    Multiply by gravitational acceleration (9.81 m/s²).

  3. 3

    Multiply by head and fluid density.

  4. 4

    Divide by 1000 to get power in kilowatts.

(flow_rate / 3600) * 9.81 * head * density / 1000

Frequently asked questions

What is hydraulic power?

It is the theoretical power needed to move fluid at a given flow rate and head, ignoring pump and motor inefficiencies.

How do I account for pump efficiency?

Divide the hydraulic power by the pump efficiency (as a decimal) to get the shaft power required.

Why is density important?

Denser fluids require more energy to lift, so power increases with density.

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Results

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Hydraulic power

0kW

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Estimate for general guidance only — verify important decisions with an appropriate professional.

How it works

Calculates the hydraulic power required to pump a fluid based on flow rate, head, and fluid density.

  1. Convert flow rate from m³/h to m³/s by dividing by 3600.
  2. Multiply by gravitational acceleration (9.81 m/s²).
  3. Multiply by head and fluid density.
  4. Divide by 1000 to get power in kilowatts.

Formulas

The math behind this calculator, written out so you can verify the result.

Hydraulic Power

P = (Q × ρ × g × H) / 1000

Power in kW equals flow rate (m³/s) times density (kg/m³) times gravity (9.81 m/s²) times head (m), divided by 1000.

Example:

Input: Q = 50 m³/h, H = 20 m, ρ = 1000 kg/m³

Calculation: (50/3600) × 1000 × 9.81 × 20 / 1000

Result: ≈ 2.73 kW

Real-world use cases

Where this calculation shows up in everyday life.

Sizing a pump motor

Estimate the minimum motor power needed for a given duty.

Example: Selecting a motor for a 50 m³/h, 20 m head water pump.

Comparing pump options

Evaluate energy requirements for different flow and head conditions.

Example: Choosing between two pumps with different efficiencies.

Energy cost estimation

Calculate power consumption to estimate operating costs.

Example: Estimating annual electricity cost for a pumping system.

Tips and common mistakes

Tips

  • Use actual fluid density for accurate results (e.g., 998 kg/m³ for water at 20°C).
  • Remember that hydraulic power is theoretical; actual power draw is higher due to losses.
  • Check units: flow rate must be in m³/h, head in meters, density in kg/m³.
  • For pump selection, divide by efficiency (e.g., 0.7 for 70%) to get shaft power.

Common Mistakes to Avoid

  • Forgetting to convert flow rate from m³/h to m³/s.
  • Using density of water for other fluids without checking.
  • Ignoring pump efficiency when sizing the motor.

Assumptions and limitations

  • Use the stated inputs and units.
  • Results are estimates for planning and education.
  • Check measurements and source data before making an important decision.