Pump Sizing Calculator

Pump Power Formula:

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

Flow Rate (Q):

GPM

Head (H):

Specific Gravity (SG):

(1 for water)

Efficiency (η):

(0-1)

Pump Power (HP):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Pump Sizing?

Pump sizing is the process of determining the appropriate power requirement for a pump based on the flow rate, head, fluid properties, and pump efficiency. Proper sizing ensures efficient operation and prevents energy waste or equipment damage.

2. How Does the Calculator Work?

The calculator uses the standard pump power 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 fluid (dimensionless, 1 for water)
\( \eta \) — Pump efficiency (decimal, 0-1)
3960 — Conversion factor (ft·lb/min per HP)

Explanation: The formula calculates the hydraulic horsepower required to move a fluid at a given flow rate against a specific head, adjusted for fluid density and pump efficiency.

3. Importance of Proper Pump Sizing

Details: Correct pump sizing is critical for energy efficiency, system reliability, and cost-effectiveness. Oversized pumps waste energy and can cause cavitation, while undersized pumps can't meet system demands.

4. Using the Calculator

Tips: Enter flow rate in GPM, head in feet, specific gravity (1 for water), and pump efficiency (typically 0.7-0.9 for centrifugal pumps). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is total dynamic head?
A: The total height a liquid must be pumped, accounting for static head, friction losses, and pressure differences.

Q2: What's a typical pump efficiency value?
A: Centrifugal pumps typically range from 70-90% efficiency (0.7-0.9). Positive displacement pumps can be 80-95% efficient.

Q3: How does specific gravity affect pump power?
A: Power is directly proportional to SG. Denser fluids (higher SG) require more power to pump at the same flow rate and head.

Q4: Should I add a safety factor to the calculated HP?
A: Typically add 10-20% safety factor to account for system uncertainties, but don't oversize excessively.

Q5: What about motor sizing?
A: Motor HP should equal or exceed the calculated pump HP, considering service factor and starting conditions.