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Free Pool Pump Horsepower Calculator

Calculate the required pump horsepower based on flow rate and total dynamic head. Size your pump correctly for optimal efficiency.

Flow Requirements

GPM needed for adequate turnover. Typical: 40-80 GPM.

System Head

Sum of static lift, friction loss, and equipment pressure. Typical: 30-60 ft.

Efficiency Factors

Typical: 60-80%

Typical: 80-90%

Enter flow and head requirements

We'll calculate the required pump horsepower.

Pool Pump Horsepower Calculator

Properly sizing your pool pump is essential for efficient operation. An undersized pump won't provide adequate circulation, while an oversized pump wastes energy and can damage equipment. This calculator uses hydraulic engineering formulas to determine the right horsepower for your system.

Understanding Pump Horsepower

Pool pump sizing involves several types of horsepower measurements:

Water Horsepower (WHP)

The theoretical power needed to move water at the required flow rate against the system head. Calculated as:

WHP = (GPM × Head in feet) ÷ 3,960

Brake Horsepower (BHP)

The actual power the pump impeller needs, accounting for pump efficiency:

BHP = WHP ÷ Pump Efficiency

Motor Horsepower

The motor rating needed, accounting for motor efficiency:

Motor HP = BHP ÷ Motor Efficiency

Understanding Total Dynamic Head (TDH)

Total Dynamic Head is the total resistance the pump must overcome, measured in feet of water:

  • Static Head: Vertical lift from water level to highest point
  • Friction Loss: Resistance from pipes, fittings, and valves
  • Equipment Loss: Pressure drop through filter, heater, chlorinator

Typical TDH Values

  • Simple above-ground: 20-30 feet
  • Standard in-ground: 30-45 feet
  • With heater/salt cell: 40-55 feet
  • Complex systems: 50-70+ feet

Common Pump Sizes

  • 1/2 HP: Small pools, simple systems
  • 3/4 HP: Small to medium in-ground pools
  • 1 HP: Standard residential pools
  • 1.5 HP: Larger pools or higher TDH
  • 2 HP: Large pools, water features
  • 3 HP: Commercial or very large residential

Pump Sizing FAQs

What size pump do I need for my pool?

It depends on your pool volume (for flow rate) and plumbing system (for head). A typical 20,000-gallon pool with standard plumbing needs a 1 to 1.5 HP pump. Use the calculator above for your specific situation.

Is a bigger pump always better?

No. Oversized pumps waste energy, can create excessive pressure that damages equipment, and may cause water to bypass the filter. Proper sizing is more important than maximum power.

What about variable-speed pumps?

Variable-speed pumps can run at lower speeds for routine filtration and ramp up when needed. Size them for maximum flow requirements, but they'll typically run at much lower (and more efficient) speeds.

How do I determine my system's TDH?

Measure static lift, calculate friction loss from pipe length and fittings, and add equipment pressure drops. Alternatively, use typical values for your pool type as a starting estimate.

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