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Whole House Fan Size Calculator
Enter your home's size and ceiling height. Get the CFM you need, the attic vent area it takes, whether your summer nights suit a whole house fan, what it saves on AC at your state's rate, and fans that fit your joists.
Updated Oct 24, 2026
- Answer a few questions
- See the math behind every number
- Get models that actually fit
Every fan this tool can recommend
Whole house fans by airflow on high, then attic-only fans. CFM, watts and vent area come from each listing or maker spec sheet; Centric Air is shown at its California Title 24 airflow.
Tamarack HV1000 R38 Ductless Whole House Fan
- 70 W max
- R38 doors
- 70 W
- 2 speeds
+1 moreFewer
- Lifetime warranty
A small two-speed fan with R38 insulated doors that seal shut when it is off, for a bedroom wing, a small home or a cold climate where the ceiling opening matters in winter.
- R38 insulated doors open and close by themselves
- Mounts on 16 or 24 in center joists, horizontal or vertical
- About 70 W (Tamarack catalog), lifetime warranty
- About 1,000 CFM: one fan covers only about 500 sq ft at 8 ft ceilings
$500 to $1,000, live price on Amazon
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QuietCool Classic CL-1500 RF Whole House Fan
- 117 W max
- 736 sq ft
- 117 W
- R5 damper
+2 moreFewer
- 14 x 14 in cutout
- 12 h timer remote
A one-speed ducted fan for a small home, a suite or the upstairs of a house: 1,472 CFM, which QuietCool rates for up to 736 sq ft.
- 117 W PSC motor
- 14 x 14 in ceiling cutout, fits 16 or 24 in on center with no joist cutting
- R5 insulated damper doors, wireless switch with a 12 hour timer
- One speed only
- Needs 1.97 sq ft of net free attic venting
$500 to $1,000, live price on Amazon
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QuietCool Classic CL-2250 RF Whole House Fan
- 250 W max
- 1,233 sq ft
- 2 speeds
- 250 W high
+2 moreFewer
- R5 damper
- 14 x 18 in cutout
A two-speed ducted fan for a condo or small single story home: 2,465 CFM on high, rated by QuietCool for up to 1,233 sq ft.
- 2,465 CFM high, 1,910 CFM low
- 250 W on high, 201 W on low
- Fits 16 or 24 in on center with no joist cutting, R5 damper doors
- Needs 3.29 sq ft of net free attic venting
- PSC motor: low speed saves less power than the Energy Saver line
$500 to $1,000, live price on Amazon
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QuietCool Energy Saver ES-3100 RF Whole House Fan
- 285 W max
- 1,541 sq ft
- ECM motor
- 81 W on low
+2 moreFewer
- R5 damper
- 14 x 22 in cutout
The ECM-motor version of the 3,100 for a small home: about the same airflow on high, and 81 W on low for all-night running.
- 3,081 CFM high, 2,020 CFM low
- ECM motor: 285 W on high, 80.8 W on low
- Fits 16 or 24 in on center with no joist cutting, R5 damper doors
- Costs more up front than the Classic CL-3100
- Needs 4.11 sq ft of net free attic venting
$1,000 to $2,000, live price on Amazon
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Show all 18 modelsShow fewer
QuietCool Classic CL-3100 RF Whole House Fan
- 299 W max
- 1,608 sq ft
- 2 speeds
- 299 W high
+2 moreFewer
- R5 damper
- 14 x 22 in cutout
A two-speed ducted fan for a small home: 3,126 CFM on high, rated by QuietCool for up to 1,608 sq ft.
- 3,126 CFM high, 2,847 CFM low
- 299 W on high, 256 W on low
- Fits 16 or 24 in on center with no joist cutting, R5 damper doors
- Needs 4.17 sq ft of net free attic venting
$500 to $1,000, live price on Amazon
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Air King 9166 20 in Whole House Window Fan
- 170 W max
- Window mount
- 3 speeds
- 170 W
+1 moreFewer
- No attic needed
No attic, or renting? A 20 in window fan exhausts the house through one window while you open others. No ceiling cut, no attic vents needed.
- 3 speeds, 1/6 HP, plugs into a 120V outlet
- About 3,560 CFM on high, 170 W (distributor spec sheet)
- Storm Guard lets you close the window behind the fan
- Takes up a window while it runs
- 1-year limited warranty
$100 to $250, live price on Amazon
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Centric Air QA-Deluxe 5500 Whole House Fan
- 2,400 sq ft
- 5,500 CFM max
- 2-speed wall switch
- Timer
+1 moreFewer
- R-5 damper
A ducted fan rated up to 5,500 CFM (3,945 CFM on the California Title 24 test) for single story homes up to 2,400 sq ft, with a 2-speed wall switch and timer.
- Fits 16 to 24 in on center joists, no framing
- R-5 insulated damper
- Low-voltage plug and play 2-speed wall switch with timer
- Centric Air does not list the wattage, so we cannot price the power
- Title 24 airflow is about 28% below the 5,500 headline
$1,000 to $2,000, live price on Amazon
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QuietCool Energy Saver ES-4700 RF Whole House Fan
- 415 W max
- 2,098 sq ft
- ECM motor
- 75 W on low
+2 moreFewer
- R5 damper
- 12 h timer remote
An ECM-motor fan for an average home: 4,195 CFM on high, rated by QuietCool for up to 2,098 sq ft, and only 75 W on low.
- 4,195 CFM high, 2,304 CFM low
- ECM motor: 415 W on high, 75 W on low
- R5 insulated damper doors, 12 hour timer remote
- The listing does not give the cutout size or joist fit; check before you buy
$1,000 to $2,000, live price on Amazon
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QuietCool Classic CL-4700 RF Whole House Fan
- 551 W max
- 2,208 sq ft
- 2 speeds
- 551 W high
+2 moreFewer
- R5 damper
- 14 x 30 in cutout
A two-speed ducted fan for an average home: 4,415 CFM on high, rated by QuietCool for up to 2,208 sq ft.
- 4,415 CFM high, 3,402 CFM low
- 551 W on high, 415 W on low
- Fits 16 or 24 in on center with no joist cutting, R5 damper doors
- Needs 5.89 sq ft of net free attic venting
$1,000 to $2,000, live price on Amazon
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Centric Air QA-Deluxe 6500 Whole House Fan
- 3,000 sq ft
- 5,878 CFM max
- 2-speed remote
- Timer
+1 moreFewer
- R5 damper
A large ducted fan: 5,878 CFM (4,478 CFM on the California Title 24 test) for single story homes up to 3,000 sq ft, with a remote and timer.
- Fits 16 or 24 in on center joists, no framing
- R5 insulated damper box
- 2-speed remote with timer
- Needs about 5.5 sq ft of attic ventilation
- Centric Air does not list the wattage, so we cannot price the power
$1,000 to $2,000, live price on Amazon
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Cool Attic 24 in Belt Drive 2-Speed Whole House Fan with Shutter
- 1,800 sq ft
- 24 in belt drive
- 2 speeds
- Ceiling shutter
+1 moreFewer
- 1/3 HP
The traditional louvered fan: a 24 in belt-drive fan that sits on the attic floor over a ceiling shutter, for houses up to 1,800 sq ft. The lowest price per CFM here.
- About 4,500 CFM high, 3,100 low (Ventamatic dealer spec)
- Belt drive, 2 speeds, made in Texas
- Ceiling shutter included
- Rough opening is 25 1/2 x 27 3/4 in, so a joist has to be cut and headered
- Louvers leak attic air in winter; plan on a shutter seal cover
$250 to $500, live price on Amazon
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QuietCool Energy Saver ES-5400 RF Whole House Fan
- 497 W max
- 2,502 sq ft
- ECM motor
- 89 W on low
+2 moreFewer
- R5 damper
- 12 h timer remote
An ECM-motor fan for an average to larger home: 5,003 CFM on high, rated by QuietCool for up to 2,502 sq ft, 89 W on low.
- 5,003 CFM high, 2,842 CFM low
- ECM motor: 497 W on high, 88.9 W on low
- R5 insulated damper doors, 12 hour timer remote
- The listing does not give the cutout size or joist fit; check before you buy
$1,000 to $2,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
QuietCool Classic CL-5400 RF Whole House Fan
- 634 W max
- 2,512 sq ft
- 2 speeds
- 634 W high
+2 moreFewer
- R5 damper
- 14 x 30 in cutout
A two-speed ducted fan for an average to larger home: 5,024 CFM on high, rated by QuietCool for up to 2,512 sq ft.
- 5,024 CFM high, 4,406 CFM low
- 634 W on high, 525 W on low
- Fits 16 or 24 in on center with no joist cutting, R5 damper doors
- Needs 6.68 sq ft of net free attic venting
$1,000 to $2,000, live price on Amazon
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QuietCool Energy Saver ES-7000 RF Whole House Fan
- 727 W max
- 3,440 sq ft
- ECM motor
- 164 W on low
+2 moreFewer
- R5 damper
- 12 h timer remote
QuietCool's biggest ECM fan for a large home: 6,878 CFM on high, rated for up to 3,440 sq ft, 164 W on low.
- 6,878 CFM high, 4,304 CFM low
- ECM motor: 727 W on high, 164 W on low
- R5 insulated damper doors, 12 hour timer remote
- The listing does not give the cutout size or joist fit; check before you buy
$1,000 to $2,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
QuietCool Classic CL-7000 RF Whole House Fan
- 1147 W max
- 3,462 sq ft
- 2 speeds
- 1,147 W high
+2 moreFewer
- R5 damper
- 12 h timer remote
QuietCool's biggest Classic fan for a large home: 6,924 CFM on high, rated for up to 3,462 sq ft.
- 6,924 CFM high, 5,518 CFM low
- R5 insulated damper doors
- Wireless switch with a 12 hour countdown timer
- 1,147 W on high, the most of any fan here
- The listing does not give the cutout size or joist fit; check before you buy
$1,000 to $2,000, live price on Amazon
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GAF Master Flow ERV6 Roof Mount Attic Fan with Thermostat
- Roof mount
- Thermostat
- Not for tile roofs
- Attic up to 2,800 sq ft
A roof-mounted power vent for an attic with no gable wall to use: 1,500 CFM with a thermostat, rated for attics up to 2,800 sq ft.
- 1,500 CFM, attic up to 2,800 sq ft
- Thermostat controller included
- Galvanized steel, built-in screen
- Cuts through the roof; not for tile roofs
- Needs intake vents, or it pulls air from the house
$100 to $250, live price on Amazon
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BINGLUX 15 in Plug-In Gable Attic Fan with Thermostat
- Gable mount
- Plug-in
- Thermostat
- Attic up to 2,500 sq ft
A plug-in gable attic fan with a 20 ft cord and thermostat, for attics up to 2,500 sq ft where there is an outlet in the attic.
- 1,650 CFM, rated for 2,500 sq ft
- Plug and play, 20 ft power cord
- Adjustable thermostat
- Needs an outlet in the attic
- Needs intake vents, or it pulls air from the house
$100 to $250, live price on Amazon
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iLIVING ILG8G14-12T Gable Attic Fan with Thermostat
- 230 W max
- Gable mount
- Thermostat
- 230 W
+1 moreFewer
- Attic up to 3,400 sq ft
An attic-only fan: mounts behind a gable vent and pushes hot attic air out when the built-in thermostat trips. It does not cool the rooms below the way a whole house fan does.
- 2,339 CFM, rated for up to 3,400 sq ft of attic
- Adjustable built-in thermostat
- 230 W, 120V
- Mounts behind an existing gable vent; needs wiring to a 120V circuit
- Needs soffit or other intake vents, or it pulls air from the house
Under $100, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Some of these links pay us a commission and some do not; each card says which. Commissions do not affect which models the tool picks or how it ranks them. See our disclosure.
How this calculator works
- Airflow. Floor area x ceiling height x air changes per hour / 60. The DOE Energy Saver guide recommends 15 to 23 air changes an hour; we use 15 as the minimum and 20 as the target. At 8 ft ceilings 15 air changes is 2 CFM per sq ft, the rate QuietCool uses for its coverage ratings.
- Attic vents. 1 sq ft of net free vent area per 750 CFM (DOE and the makers). Where a maker publishes its own figure for a fan, we use that.
- Fit. Fans the maker says fit 16 or 24 in on center joists pass for that spacing. A louvered 24 in fan needs a wider opening, so it shows only if you will cut and header a joist. Fans whose listing does not state joist fit pass with a note to check.
- Climate. A whole house fan only cools when outdoor air is cooler than indoors. Your state fills in a rough guess for summer nights, which you can change; it sets default hours and the fit verdict.
- Savings. AC watts x AC hours replaced, minus fan watts on high x fan hours, at your state's average residential rate (EIA). All three inputs are editable. Fans whose maker publishes no wattage show no savings.
- Attic fans. 0.7 CFM per sq ft of attic floor and 1 sq ft of soffit intake per 300 CFM, the power vent rules of HVI and attic vent makers like GAF Master Flow and Air Vent. We match on each maker's attic area rating.
Worked examples
1,800 sq ft ranch in California, cool nights
- 1,800 sq ft, 8 ft ceilings
- Nights below 65 F, California rate
- Quiet ducted, 24 in joists
- 3,300 W AC, 400 AC hours replaced, fan 600 hours
4,800 CFM. Best fit: QuietCool CL-5400, about $306 a season saved.
14,400 cu ft x 20 air changes / 60 = 4,800 CFM (3,600 at the 15 air change minimum). The QuietCool CL-5400 moves 5,024 CFM on high, fits 24 in joists and needs 6.68 sq ft of attic vent area. 3,300 W x 400 h of AC skipped is 1,320 kWh, about $430 at 32.5 cents. The fan uses 634 W x 600 h = 380 kWh, about $124. Net: about $306 a season.
1,400 sq ft with 9 ft ceilings in Ohio, few attic vents
- 1,400 sq ft, 9 ft ceilings
- Nights 65 to 75 F, Ohio rate
- 16 in joists, will add vents
- 250 AC hours replaced, fan 450 hours
4,200 CFM. Best fit: QuietCool CL-4700, plus one box of soffit vents. About $98 a season.
12,600 cu ft x 20 / 60 = 4,200 CFM. The CL-4700 gives 4,415 CFM, fits 16 in joists with a 14 x 30 in cutout and needs 5.89 sq ft of net free vent area. One box of 24 Air Vent soffit vents at 56 sq in each adds 9.3 sq ft. Savings: 825 kWh of AC (about $140 at 17 cents) minus 248 kWh of fan (about $42) = about $98.
2,000 sq ft in Houston, warm muggy nights
- 2,000 sq ft, 8 ft ceilings
- Nights above 75 F, Texas rate
- 75 AC hours replaced, fan 150 hours
5,333 CFM, but only about $12 a season. Spend on the AC instead.
16,000 cu ft x 20 / 60 = 5,333 CFM, which takes a QuietCool CL-7000 (6,924 CFM). But a whole house fan only cools when outside air is cooler than inside. With about 75 useful hours a season it saves about $38 of AC and uses about $27 of fan power on high. The tool says so instead of selling you a fan.
Frequently asked questions
What size whole house fan do I need?
Multiply square feet by ceiling height, then by 15 to 20 air changes an hour, and divide by 60. The DOE recommends 15 to 23 air changes. At 8 ft ceilings that is 2 to 3 CFM per sq ft: a 1,500 sq ft home needs about 3,000 to 4,000 CFM, and 2,000 sq ft needs about 4,000 to 5,300.
How much attic venting does a whole house fan need?
About 1 sq ft of net free vent area for every 750 CFM, the figure DOE and the makers use. A 4,500 CFM fan needs about 6 sq ft. Net free area is printed on each vent; an Air Vent 16 x 8 in soffit vent is 56 sq in. Too little vent area pushes hot air back down into the house and cuts the fan's airflow.
Do whole house fans really save money?
Where summer nights are cool, yes. The fans here draw about 70 to 1,150 W on high, where a 3 ton central AC draws about 3,300 W. In a climate with 400 evening hours the fan can replace, that is a few hundred dollars a season. Where nights stay above 75 F or are humid, it may save almost nothing.
What is the difference between a whole house fan and an attic fan?
A whole house fan sits in the ceiling and pulls cool outside air in through open windows, pushing house air out through the attic. An attic fan mounts in a gable or the roof and only exhausts hot attic air. It does not cool the rooms directly, and without enough soffit intake it can pull cooled air up out of the house.
Are whole house fans loud?
Ducted models like QuietCool and Centric Air hang the motor in the attic and run a flexible duct to the ceiling grille, so the motor is away from the opening. The traditional belt-drive type sits right on the joists above a big louvered shutter. Low speed on any fan is quieter than high.
Can I run a whole house fan with the windows closed?
No. The fan needs open windows to pull air from. With the house closed up it can pull exhaust back down a gas water heater, furnace or fireplace flue. Open windows first, and open more on the side the breeze comes from.
What happens to a whole house fan in winter?
Insulated models close off the ceiling: QuietCool and Centric Air use R5 damper doors, Tamarack R38 doors. A louvered belt-drive fan has a metal shutter, so a removable cover goes over it from the house side for winter.
Do whole house fans work in humid climates?
Poorly. They bring in outdoor air as it is, so muggy night air makes the house muggy, and the AC then has to remove that moisture. They work best where nights cool off and air is dry, like most of the West, the Mountain states and northern states.
Marcus Reed
Founder and Editor, CrunchYourDollars
Marcus Reed builds the sizing tools on CrunchYourDollars. He is a software engineer with a long-running PC hardware and power supply habit, which is where the watts, watt-hours and surge math on this site comes from. Product specs are pulled from manufacturer data sheets, electricity rates from the U.S. Energy Information Administration, and water chemistry rules from the Water Quality Association. He is not a licensed electrician or plumber: the tools show the math and the matching models so you can make the call, and anything involving your electrical panel should be checked by a licensed pro.
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