Ventilation Calculator

How to Calculate

Step 1: Measure

Measure the length and width of the attic floor space to be ventilated.

Step 2: Calculate

Enter the length and width or the total square footage of the attic floor space to be ventilated.
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Step 3: Identify

See recommended quantities below for each GAF Ventilation Product (typically rounded up).

Let’s get started

Use this calculator to help determine the proper amount of attic ventilation based on U.S. FHA 1/300 guidelines.*

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Suggestions for 900 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.
And
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

ProductLineal Feet Required
Cobra® RidgeRunner®31'
Cobra® Rigid Vent 3™22'
Cobra® SnowCountry®22'
Cobra® SnowCountry® Advanced22'
Cobra® Hip Vent43'
TruSlate® Ridge Vent43'

Product

Cobra® RidgeRunner®

Lineal Feet Required

31'

Product

Cobra® Rigid Vent 3™

Lineal Feet Required

22'

Product

Cobra® SnowCountry®

Lineal Feet Required

22'

Product

Cobra® SnowCountry® Advanced

Lineal Feet Required

22'

Product

Cobra® Hip Vent

Lineal Feet Required

22'

Product

TruSlate® Ridge Vent

Lineal Feet Required

22'

ProductLineal Feet Required
Cobra® Exhaust Vent - Hand Nailable31'
Cobra® Exhaust Vent - Nail Gunnable22'

Product

Cobra® Exhaust Vent - Hand Nailable

Lineal Feet Required

31'

Product

Cobra® Exhaust Vent - Nail Gunnable

Lineal Feet Required

22'

ProductLineal Feet Required
AR1031'

Product

AR10

Lineal Feet Required

31'

ProductNumber Required
RT65 Plastic Square - Top31
IR61 Plastic Slant - Back31
R50/RV50 Metal Utility31
IR65 Plastic Slant - Back31
SSB960 Metal Super Slant - Back31
HCD144 High-Capacity Dome Vent31

Product

RT65 Plastic Square - Top

Number Required

31

Product

IR61 Plastic Slant - Back

Number Required

31

Product

R50/RV50 Metal Utility

Number Required

31

Product

IR65 Plastic Slant - Back

Number Required

31

Product

SSB960 Metal Super Slant - Back

Number Required

31

Product

HCD144 High-Capacity Dome Vent

Number Required

31

Intake Ventilation

ProductLineal Feet Required
Cobra IntakePro®31'

Product

Cobra IntakePro®

Lineal Feet Required

31'

Product

Cobra® Fascia Vent (Mesh Roll) 1"

Lineal Feet Required

22'

Product

Cobra® Fascia Vent (Mesh Roll) 1.5"

Lineal Feet Required

22'

ProductNumber Required
LSV8 Metal Continuous Soffit Vents (Lineal Feet)31'
EAP 4x12 Plastic Soffit Vents31
EAC 16x4 Metal Soffit Vents31
EAC 16x8 Metal Soffit Vents31
EmberShield® Closeable Soffit Vents31

Product

LSV8 Metal Continuous Soffit Vents

Number Required

31

Product

EAP 4x12 Plastic Soffit Vents

Number Required

22

Product

EAC 16x4 Metal Soffit Vents

Number Required

22

Product

EAC 16x8 Metal Soffit Vents

Number Required

22

Product

EmberShield® Closeable Soffit Vents

Number Required

22

Intake or Exhaust Ventilation

Note: Gable louvers are typically installed in pairs

ProductNumber Required
DA 12x1231
DA 12x1831
DA 14x2431
DA 18x2431
DA 24x3031

Product

DA 12x12

Number Required

31

Product

DA 12x18

Number Required

31

Product

DA 14x24

Number Required

31

Product

DA 18x24

Number Required

32

Product

DA 24x30

Number Required

33

ProductNumber Required
SL 8x831
SL 12x1231
SL 12x1831
SL 18x2431

Product

SL 8x8

Number Required

34

Product

SL 12x12

Number Required

35

Product

SL 12x18

Number Required

36

Product

SL 14x24

Number Required

37

Product

SL 18x24

Number Required

38

ProductNumber Required
RLSC 2"31
RLSC 3"31
RLSC 4"31

Product

RLSC 2"

Number Required

39

Product

RLSC 3"

Number Required

40

Product

RLSC 4"

Number Required

41

Exhaust Ventilation

ProductNumber Required
ERV431
ERV5 & Wi-Fi ERV5QCT22
ERV622
EZ Cool™ EZCR122

Product

ERV4

Number Required

31

Product

ERV5 & Wi-Fi ERV5QCT

Number Required

22

Product

ERV6

Number Required

31

Product

EZ Cool™ EZCR1

Number Required

31

ProductNumber Required
EGV5 & Wi-Fi EGV5QCT31
EGV622
EZ Cool™ EZCG122

Product

EGV5 & Wi-Fi EGV5QCT

Number Required

31

Product

EGV6

Number Required

31

Product

EZ Cool™ EZCG1

Number Required

31

ProductNumber Required
Solar & Dual-Powered Roof (ERVSOLAR / ERVHYBRID)31
Solar-Powered Gable (PGSOLAR)22
High-Power Solar & Dual-Powered Roof (PRSOLAR2 / PRHYBRID2)22

Product

Solar & Dual-Powered Roof (ERVSOLAR / ERVHYBRID)

Number Required

31

Product

Solar-Powered Gable (PGSOLAR)

Number Required

31

Product

High-Power Solar & Dual-Powered Roof (PRSOLAR2 / PRHYBRID2)

Number Required

31

ProductNumber Required
12"31
14"22

Product

12"

Number Required

31

Product

14"

Number Required

31

Intake Ventilation

ProductLineal Feet Required
with ERV431'
with ERV5 & Wi-Fi ERV5QCT22'
with ERV631'
with EZ Cool™ EZCR131'
with EGV5 & Wi-Fi EGV5QCT22'
with EGV631'
with EZ Cool™ EZCG131'
with Solar & Dual-Powered Roof22'
with Solar-Powered Gable22'
with High-Power Solar & Dual-Powered Roof22'
with 12" Wind Turbine22'
with 14" Wind Turbine22'

Product

with ERV4

Lineal Feet Required

31'

Product

with ERV5 & Wi-Fi ERV5QCT

Lineal Feet Required

31'

Product

with ERV6

Lineal Feet Required

31'

Product

with EZ Cool™ EZCR1

Lineal Feet Required

31'

Product

with EGV5 & Wi-Fi EGV5QCT

Lineal Feet Required

31'

Product

with EGV6

Lineal Feet Required

31'

Product

with EZ Cool™ EZCG1

Lineal Feet Required

31'

Product

with Solar & Dual-Powered Roof

Lineal Feet Required

31'

Product

with Solar-Powered Gable

Lineal Feet Required

31'

Product

with High-Power Solar & Dual-Powered Roof

Lineal Feet Required

31'

Product

with 12" Wind Turbine

Lineal Feet Required

31'

Product

with 14" Wind Turbine

Lineal Feet Required

31'

ProductLineal Feet Required
with ERV431'
with ERV5 & Wi-Fi ERV5QCT22'
with ERV631'
with EZ Cool™ EZCR131'
with EGV5 & Wi-Fi EGV5QCT22'
with EGV631'
with EZ Cool™ EZCG131'
with Solar & Dual-Powered Roof22'
with Solar-Powered Gable22'
with High-Power Solar & Dual-Powered Roof22'
with 12" Wind Turbine22'
with 14" Wind Turbine22'

Product

with ERV4

Lineal Feet Required

31'

Product

with ERV5 & Wi-Fi ERV5QCT

Lineal Feet Required

31'

Product

with ERV6

Lineal Feet Required

31'

Product

with EZ Cool™ EZCR1

Lineal Feet Required

31'

Product

with EGV5 & Wi-Fi EGV5QCT

Lineal Feet Required

31'

Product

with EGV6

Lineal Feet Required

31'

Product

with EZ Cool™ EZCG1

Lineal Feet Required

31'

Product

with Solar & Dual-Powered Roof

Lineal Feet Required

31'

Product

with Solar-Powered Gable

Lineal Feet Required

40'

Product

with High-Power Solar & Dual-Powered Roof

Lineal Feet Required

31'

Product

with 12" Wind Turbine

Lineal Feet Required

31'

Product

with 14" Wind Turbine

Lineal Feet Required

31'

ProductNumber Required
with ERV431
with ERV5 & Wi-Fi ERV5QCT22
with ERV631
with EZ Cool™ EZCR131
with EGV5 & Wi-Fi EGV5QCT22
with EGV631
with EZ Cool™ EZCG131
with Solar & Dual-Powered Roof22
with Solar-Powered Gable22
with High-Power Solar & Dual-Powered Roof22
with 12" Wind Turbine22
with 14" Wind Turbine22

Product

with ERV4

Number Required

31

Product

with ERV5 & Wi-Fi ERV5QCT

Number Required

31

Product

with ERV6

Number Required

31

Product

with EZ Cool™ EZCR1

Number Required

31

Product

with EGV5 & Wi-Fi EGV5QCT

Number Required

31

Product

with EGV6

Number Required

31

Product

with EZ Cool™ EZCG1

Number Required

31

Product

with Solar & Dual-Powered Roof

Number Required

31

Product

with Solar-Powered Gable

Number Required

49

Product

with High-Power Solar & Dual-Powered Roof

Number Required

31

Product

with 12" Wind Turbine

Number Required

31

Product

with 14" Wind Turbine

Number Required

31

ProductNumber Required
with ERV431
with ERV5 & Wi-Fi ERV5QCT22
with ERV631
with EZ Cool™ EZCR131
with EGV5 & Wi-Fi EGV5QCT22
with EGV631
with EZ Cool™ EZCG131
with Solar & Dual-Powered Roof22
with Solar-Powered Gable22
with High-Power Solar & Dual-Powered Roof22
with 12" Wind Turbine22
with 14" Wind Turbine22

Product

with ERV4

Number Required

31

Product

with ERV5 & Wi-Fi ERV5QCT

Number Required

31

Product

with ERV6

Number Required

31

Product

with EZ Cool™ EZCR1

Number Required

31

Product

with EGV5 & Wi-Fi EGV5QCT

Number Required

31

Product

with EGV6

Number Required

31

Product

with EZ Cool™ EZCG1

Number Required

31

Product

with Solar & Dual-Powered Roof

Number Required

31

Product

with Solar-Powered Gable

Number Required

58

Product

with High-Power Solar & Dual-Powered Roof

Number Required

31

Product

with 12" Wind Turbine

Number Required

31

Product

with 14" Wind Turbine

Number Required

31

ProductNumber Required
with ERV431
with ERV5 & Wi-Fi ERV5QCT22
with ERV631
with EZ Cool™ EZCR131
with EGV5 & Wi-Fi EGV5QCT22
with EGV631
with EZ Cool™ EZCG131
with Solar & Dual-Powered Roof22
with Solar-Powered Gable22
with High-Power Solar & Dual-Powered Roof22
with 12" Wind Turbine22
with 14" Wind Turbine22

Product

with ERV4

Number Required

31

Product

with ERV5 & Wi-Fi ERV5QCT

Number Required

31

with ERV6

Number Required

31

with EZ Cool™ EZCR1

Number Required

31

with EGV5 & Wi-Fi EGV5QCT

Number Required

31

with EZ Cool™ EZCG1

Number Required

31

with Solar & Dual-Powered Roof

Number Required

31

with Solar-Powered Gable

Number Required

67

with High-Power Solar & Dual-Powered Roof

Number Required

31

with 12" Wind Turbine

Number Required

31

with 14" Wind Turbine

Number Required

31

ProductNumber Required
with ERV431
with ERV5 & Wi-Fi ERV5QCT22
with ERV631
with EZ Cool™ EZCR131
with EGV5 & Wi-Fi EGV5QCT22
with EGV631
with EZ Cool™ EZCG131
with Solar & Dual-Powered Roof22
with Solar-Powered Gable22
with High-Power Solar & Dual-Powered Roof22
with 12" Wind Turbine22
with 14" Wind Turbine22

Product

with ERV4

Number Required

31

Product

with ERV5 & Wi-Fi ERV5QCT

Number Required

31

Product

with ERV6

Number Required

31

Product

with EZ Cool™ EZCR1

Number Required

31

Product

with EGV5 & Wi-Fi EGV5QCT

Number Required

31

Product

with EGV6

Number Required

31

Product

with EZ Cool™ EZCG1

Number Required

31

Product

with Solar & Dual-Powered Roof

Number Required

31

Product

with Solar-Powered Gable

Number Required

75

Product

with High-Power Solar & Dual-Powered Roof

Number Required

31

Product

with 12" Wind Turbine

Number Required

31

Product

with 14" Wind Turbine

Number Required

31

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.

Master Flow Roof Louver SSB960A - Aluminum Slant-Back
Master Flow™ Roof Louver SSB960A - Aluminum Slant-Back
See product
Master Flow GreenMachine High-Power Solar Roof Vent - PRSOLAR2
Master Flow™ GreenMachine™ High-Power Solar Roof Vent - PRSOLAR2
See product
Master Flow Power Attic Vent ERV5 - Roof Mount
Master Flow™ Power Attic Vent ERV5 - Roof Mount
See product
Diagram of intake and exhaust ventilation

The 1/300 balanced attic ventilation rule

Proper attic ventilation consists of a balance between air intake (at or near your soffits) and air exhaust (at or near your roof ridge). The U.S. Federal Housing authority recommends a minimum of 1 square foot of attic ventilation (evenly split between intake and exhaust) for every 300 square feet of attic floor space. Always have a balanced ventilation system. In no case should the amount of exhaust ventilation exceed the amount of intake ventilation.
Watch video
*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.
Examples of static, power, and mechanical attic vents

Learn about attic vent options

Are you confused about the many attic ventilation solutions available? Curious why one roof would get ridge ventilation and another would incorporate power vents or a roof louver? Watch this video for a great introduction to the art and science of choosing the right attic ventilation components for your roof.
Watch video Learn more

Your top attic ventilation questions answered

Image showing why you should use attic ventilation

How to Ventilate an Attic - How Attic Ventilation Works | GAF Roofing

What is attic ventilation? Learn how attics are ventilated.

How to Select Products for Your Attic Ventilation System | GAF Roofing

Determine which ventilation products are best for your roofing project.

How to Plan a Balanced Attic Ventilation System | GAF Roofing Materials

In this video, you will learn how to calculate a balanced attic ventilation system.

How to Avoid Common Attic Ventilation Installation Mistakes | GAF Roofing

When planning and installing a balanced attic ventilation system, it is important to understand and avoid these common mistakes that may reduce the effectiveness of the system.

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