Attic Ventilation Calculator

Attic Ventilation Calculator

How to Calculate

1. Measure
Measure the length and width of the attic floor space to be ventilated.
2. Calculate
Enter the length and width or the total square footage of the attic floor space to be ventilated.
3. Identify
See recommended quantities below for each GAF Ventilation Product (typically rounded up).
Use this calculator to help determine the proper amount of attic ventilation based on U.S. FHA 1/300 guidelines.*
Please enter a valid number
Please enter a valid number

Suggestions for ' x ' Area

Suggestions for sq. ft. Area

Numbers shown represent the recommended total number of units required for a single product.
384 Minimum Sq. In. of Net Free Area of exhaust needed at or near the ridge.
384 Minimum Sq. In. of Net Free Area of intake needed at or near the soffit.

Please Note:

Some local building codes require the 1/150 attic ventilation rule, which increases the minimum attic ventilation needed. Always consult local building code requirements in your area for details.
Note: N/R = not recommended

Exhaust Ventilation

cobra® & other GAF plastic vents (Lineal Feet)
Cobra® Exhaust Vent - Mesh Rolls (Lineal Feet)
Master Flow® Aluminum Ridge Vent (Lineal Feet)
Master Flow® Roof Louvers (# of Vents)

Intake Ventilation

Cobra® Intake Vents (Lineal Feet)
Master Flow® Soffit/Undereave Vents (# of Vents, except for LSV8)

Intake or Exhaust Ventilation

Note: Gable louvers are typically installed in pairs
Master Flow® Metal Gable Wall Louvers (# of Vents)
Master Flow® Plastic Gable Wall Louvers (# of Vents)
Master Flow® Plastic Circular Louvers (# of Vents)

Exhaust Ventilation

Master Flow® Power Attic Vents - Roof Mount (# of Vents)
Master Flow® Power Attic Vents - Gable Mount (# of Vents)
Master Flow® Green Machine Solar & Dual-Powered Vents (# of Vents)
Master Flow® Wind Turbines (# of Vents)

Intake Ventilation

Cobra IntakePro® (Lineal Feet)
LSV8 Metal Continuous Soffit Vents (Lineal Feet)
EAP 4x12 Plastic Soffit Vents (# Of Vents)
EAC 16x4 Metal Soffit Vents (# Of Vents)
EAC 16x8 Metal Soffit Vents (# Of Vents)
EmberShield® Closeable Soffit Vents (# Of Vents)


Attic Ventilation & Vent Products

To find the right attic ventilation solution for your roofing project, choose from a complete line of ridge and hip vents, electric and solar power vents, roof and gable louvers, wind turbines, intake vents, and more, all from GAF.


View all products

Cobra® Rigid Vent 3

Cobra® SnowCountry® Advanced

Cobra® IntakePro®

Master Flow® Roof Louver SSB960A - Aluminum Slant-Back

Master Flow® Power Attic Vent ERV5 - Roof Mount

Master Flow® GreenMachine High-Power Solar Roof Vent - PRSOLAR2

*Note: The 1/300 rule is a general rule and does not apply to all situations. Local building codes, when stricter, take precedence. Always consult a design professional for cathedral ceilings, insulated roof decks, etc.

Your Top Attic Ventilation Questions Answered

How to Ventilate an Attic - How Attic Ventilation Works | GAF Roofing
How to Select Products for Your Attic Ventilation System | GAF Roofing
How to Plan a Balanced Attic Ventilation System | GAF Roofing Materials
How to Avoid Common Attic Ventilation Installation Mistakes | GAF Roofing
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