Pump Horsepower Calculator

Pump Horsepower Formula:

\[ HP = \frac{Q \times H \times SG}{3960 \times \eta} \]

Flow Rate (Q):

GPM

Head (H):

Specific Gravity (SG):

Efficiency (η):

decimal (0-1)

Pump Horsepower (HP):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Pump Horsepower?

Pump horsepower (HP) is the power required to move a fluid at a specified flow rate against a specified head, accounting for the fluid's specific gravity and the pump's efficiency. It's a crucial parameter in pump selection and system design.

2. How Does the Calculator Work?

The calculator uses the pump horsepower formula:

\[ HP = \frac{Q \times H \times SG}{3960 \times \eta} \]

Where:

\( Q \) — Flow rate (gallons per minute, GPM)
\( H \) — Total dynamic head (feet, ft)
\( SG \) — Specific gravity of the fluid (dimensionless)
\( \eta \) — Pump efficiency (decimal, 0-1)
3960 — Conversion factor (ft·lb/min per HP)

Explanation: The equation calculates the theoretical power required to move the fluid, then divides by the pump's efficiency to get actual required horsepower.

3. Importance of Pump Horsepower Calculation

Details: Accurate horsepower calculation ensures proper pump selection, prevents motor overload, and optimizes energy consumption in fluid systems.

4. Using the Calculator

Tips: Enter flow rate in GPM, head in feet, specific gravity (1.0 for water), and pump efficiency as a decimal (e.g., 0.75 for 75%). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between brake horsepower and water horsepower?
A: Water horsepower is the theoretical power needed to move the fluid, while brake horsepower includes the pump's inefficiency (BHP = WHP/η).

Q2: How do I estimate pump efficiency?
A: Typical centrifugal pump efficiencies range from 50-85%. Smaller pumps tend to have lower efficiencies. Consult manufacturer curves for specific pumps.

Q3: What if my fluid has high viscosity?
A: This formula works best for water-like fluids. For viscous fluids, additional correction factors are needed.

Q4: How does specific gravity affect horsepower?
A: Higher SG fluids require more power - horsepower is directly proportional to specific gravity.

Q5: What's the 3960 constant?
A: It's the conversion factor: 1 HP = 33,000 ft·lb/min, and 1 gallon of water weighs 8.34 lb (33,000/8.34 ≈ 3960).