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Whole House Fan Calculator — CFM Sizing Tool

Calculate CFM needed for whole house ventilation by home square footage and volume

Units

Required CFM

5,333

Fan

30" Fan

Savings

$1,117/yr

Fan Sizing

Recommended Fan
30" Fan
6,000 CFM (5,333 needed)
Power
350W
Annual Cost
$35/yr

Cost & Savings

Fan Cost$500
Installation$500 – $1,500
Total$1,000 – $2,000
Fan Annual Cost$35/yr
AC Annual Cost$1,152/yr
Annual Savings$1,117/yr

What You'll Need

Broan-NuTone EVOLVE Exhaust Fan 50-80-110 Selectable CFM

Broan-NuTone EVOLVE Exhaust Fan 50-80-110 Selectable CFM

$80-$1204.5
View on Amazon
Broan-NuTone Wall Ducting Kit 4" 9-Piece Flexible

Broan-NuTone Wall Ducting Kit 4" 9-Piece Flexible

$12-$184.4
View on Amazon

HoldPeak 866B Digital Anemometer Wind Speed Meter

$58-$664.6
View on Amazon
Wooster Pro/Doo-Z Roller Cover 9" 3-Pack

Wooster Pro/Doo-Z Roller Cover 9" 3-Pack

$8-$124.8
View on Amazon

Painters Tape 1 inch Multi-Surface 10-Pack

$22-$264.9
View on Amazon
Wagner Spraytech FLEXiO 590 HVLP Paint Sprayer

Wagner Spraytech FLEXiO 590 HVLP Paint Sprayer

$55-$754.4
View on Amazon
Broan-NuTone EVOLVE Exhaust Fan 50-80-110 Selectable CFM

Broan-NuTone EVOLVE Exhaust Fan 50-80-110 Selectable CFM

$80-$1204.5
View on Amazon
Broan-NuTone Wall Ducting Kit 4" 9-Piece Flexible

Broan-NuTone Wall Ducting Kit 4" 9-Piece Flexible

$12-$184.4
View on Amazon

HoldPeak 866B Digital Anemometer Wind Speed Meter

$58-$664.6
View on Amazon
Wooster Pro/Doo-Z Roller Cover 9" 3-Pack

Wooster Pro/Doo-Z Roller Cover 9" 3-Pack

$8-$124.8
View on Amazon

Painters Tape 1 inch Multi-Surface 10-Pack

$22-$264.9
View on Amazon
Wagner Spraytech FLEXiO 590 HVLP Paint Sprayer

Wagner Spraytech FLEXiO 590 HVLP Paint Sprayer

$55-$754.4
View on Amazon

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Example Calculations

12,000 sq ft Single Story

Inputs

Home2,000 sq ft
Ceiling8 ft
Stories1

Result

Required CFM5,333 CFM (30" fan)

2,000 × 8 = 16,000 cu ft / 3 min = 5,333 CFM. A 30" fan (6,000 CFM) recommended.

22,500 sq ft Two Story

Inputs

Home2,500 sq ft
Ceiling9 ft
Stories2

Result

Required CFM15,000 CFM (48" fan)

2,500 × 9 × 2 = 45,000 cu ft / 3 = 15,000 CFM. A 48" fan (14,000 CFM) needed.

Frequently Asked Questions

Q

How do I calculate CFM for a whole house fan?

Multiply your home volume (sq ft × ceiling height × stories) and divide by 3 for a complete air exchange every 3 minutes. A 2,000 sq ft home with 8 ft ceilings needs about 5,333 CFM.

  • Formula: Home Volume (cu ft) / 3 minutes = required CFM
  • 2,000 sq ft × 8 ft ceiling = 16,000 cu ft / 3 = 5,333 CFM
  • Multi-story: multiply volume by number of stories
  • Round up to next fan size (4500, 6000, 8000, 10000, 14000 CFM)
Q

How much can a whole house fan save on AC costs?

A whole house fan uses 200–900 watts vs 3,500–5,000 watts for central AC. Annual savings range from $200–$600. The fan pays for itself in 1–3 years.

  • Whole house fan: $0.01–$0.05 per hour to operate
  • Central AC: $0.30–$0.60 per hour for a 3-ton system
  • Best when outdoor temp drops below 80°F in evenings
  • Can reduce AC usage by 50–90% in dry climates
Q

How much open window area do I need?

You need 1 square foot of open window area for every 750 CFM. A 6,000 CFM fan needs at least 8 sq ft of open window area to prevent back-pressure and noise.

  • 6,000 CFM fan needs 8+ sq ft of open window NFA
  • Open 4–6 windows on the windward side for cross-ventilation
  • Insufficient window area causes whistling noise and reduced airflow
  • Screen reduces NFA by 30–50%; account for this in calculations
Q

How much does a whole house fan cost to install?

A whole house fan costs $300–$1,600 for the unit plus $500–$1,500 for professional installation. Total ranges from $800–$3,100 depending on fan size and attic access.

  • 24" fan (4,500 CFM): $300–$500 for homes under 1,500 sq ft
  • 30" fan (6,000 CFM): $500–$800, most common residential size
  • 36–42" fan (8,000–10,000 CFM): $800–$1,100 for larger homes
  • Installation: $500–$1,500 including ceiling opening, wiring, and damper

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Last Updated: Mar 19, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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