Pump Motor kW Calculator

Pump Motor Power Formula:

\[ P_e = \frac{Q \times H \times \rho \times 0.746}{3960 \times \eta} \]

Flow Rate (Q):

GPM

Head (H):

Density (ρ):

lb/gal

Efficiency (η):

Motor Power (P_e):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is a Pump Motor kW Calculator?

Definition: This calculator estimates the required motor power (in kilowatts) for a pump based on flow rate, head, fluid density, and pump efficiency.

Purpose: It helps engineers and technicians properly size pump motors for various fluid transfer applications.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ P_e = \frac{Q \times H \times \rho \times 0.746}{3960 \times \eta} \]

Where:

\( P_e \) — Motor power (kW)
\( Q \) — Flow rate (gallons per minute)
\( H \) — Total head (feet)
\( \rho \) — Fluid density (pounds per gallon)
\( \eta \) — Pump efficiency (0-1)

Explanation: The formula converts hydraulic power to mechanical power, accounting for pump efficiency.

3. Importance of Proper Motor Sizing

Details: Correct motor sizing ensures efficient operation, prevents overload conditions, and reduces energy costs.

4. Using the Calculator

Tips: Enter flow rate in GPM, head in feet, fluid density (default 8.34 lb/gal for water), and pump efficiency (default 0.85). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical pump efficiency value?
A: Centrifugal pumps typically range from 0.7-0.9 (70-90% efficient), depending on size and design.

Q2: Why is density important in the calculation?
A: Denser fluids require more power to pump at the same flow rate and head.

Q3: What's the 0.746 factor in the formula?
A: This converts horsepower to kilowatts (1 HP = 0.746 kW).

Q4: How do I account for motor efficiency?
A: Divide the calculated power by the motor efficiency (typically 0.9-0.95) to get required input power.

Q5: What safety factor should I add?
A: Industry standards typically add 10-25% to the calculated power for safety margins.