To calculate how many CFM of airflow is required to properly ventilate any room in your home, use the following calculation.

For an 8 foot ceiling take the square footage of the room and multiply it by 1.1. (Example – 10' x 10' room with 8' ceilings: 10' x 10' = 100 square feet x 1.1 = 110 CFM’s)

For any ceiling over 8 feet, take the height of the ceiling and multiply by .1375. Take this figure and multiply by the square footage of the room. This will equal the recommended CFMs. (Example – 10' x 12' room with 9' ceilings: 9' x .1375 =1.24 x 120 square feet = 149 CFMs.)

Both calculations will give you the minimum recommended CFM

Bathroom fan sizing chart

Bathroom (to achieve 8 ACH as per HVI)

Equivalent duct length

Sq ft

20 feet

40 feet

60 feet

80 feet

100 feet

30

FV-05VQ

FV-05VQ

FV-05VQ

FV-05VQ

FV-05VQ

40

FV-05VQ

FV-05VQ

FV-05VQ

FV-05VQ

FV-05VQ

50

FV-05VQ

FV-05VQ

FV-08VQ or FV-08VQL

FV-08VQ or FV-08VQL

FV-08VQ or FV-08VQL

60

FV-08VQ or FV-08VQL

FV-08VQ or FV-08VQL

FV-08VQ or FV-08VQL

FV-11VQ or FV-11VQL

FV-11VQ or FV-11VQL

70

FV-08VQ, FV-08VQL, 
FV-11VH or FV-11VHL

FV-08VQ, FV-08VQL, 
FV-11VH or FV-11VHL

FV-11VQ, FV-11VQL, 
FV-11VH or FV-11VHL

FV-11VQ, FV-11VQL, 
FV-11VH or FV-11VHL

FV-11VQ, FV-11VQL, 
FV-11VH or FV-11VHL

80

FV-11VQ, FV-11VQL, 
FV-11VH or FV-11VHL

FV-11VQ, FV-11VQL, 
FV-11VH or FV-11VHL

FV-11VQ, FV-11VQL, 
FV-11VH or FV-11VHL

FV-15VQ or FV-15VQL

FV-15VQ or FV-15VQL

90

FV-11VQ, FV-11VQL, 
FV-11VH or FV-11VHL

FV-11VQ, FV-11VQL, 
FV-11VH or FV-11VHL

FV-15VQ or FV-15VQL

FV-15VQ or FV-15VQL

FV-20VQ or FV-15VQ or
FV-15VQL

100

FV-11VQ, FV-11VQL, 
FV-11VH or FV-11VHL

FV-15VQ or FV-15VQL

FV-15VQ or FV-15VQL

FV-20VQ or FV-15VQ or
FV-15VQL

FV-20VQ or FV-15VQ or
FV-15VQL

140

FV-15VQ or FV-15VQL

FV-20VQ

FV-20VQ

FV-20VQ

FV-20VQ

180

FV-20VQ or FV-11VQ (x2)

FV-20VQ or FV-11VQ (x2)

FV-20VQ or FV-11VQ (x2)

FV-20VQ or FV-11VQ (x2)

FV-30VQ or FV-20VQ (x2) or
FV-15VQ (x2)

240

FV-20VQ or FV-11VQ (x2)

FV-20VQ or FV-11VQ (x2)

FV-30VQ or FV-20VQ (x2) or
FV-15VQ (x2)

FV-40VQ or FV-20VQ (x2) or
FV-15VQ (x2)

FV-40VQ or FV-20VQ (x2) or
FV-15VQ (x2)

300

FV-40VQ or FV-20VQ (x2) or
FV-15VQ (x2)

FV-40VQ or FV-20VQ (x2)

FV-40VQ or FV-20VQ (x2)

FV-20VQ (x2)

FV-20VQ (x2)