Model "A" Soffit Vent
Soffit Ventilation Calculator
(Soffit "B" Calculator, Soffit "C" Calculator)
Based on the 1/150 or 1/300 Rule
To determine how many Model "A" soffit vents of a given length (inches) are required to properly ventilate an attic space:

If you know the length &
width of the attic floor:
OR
If you know the square footage of the attic floor:

1. Enter the length of
the building in feet
2. Enter the width of
the building in feet
3. Choose the desired vent


4.

vents required - 1/300 rule

5.

vents required - 1/150 rule

1.Enter the total area of attic
in square feet



2.Choose the desired vent


3.

vents required - 1/300 rule

4.

vents required - 1/150 rule

Application: One vent for intake per:

Model
Sq. Feet
of Floor
1/150
Sq. Feet
of Floor
1/300
Net Free
Vent Area
in Sq. Inches
Net Free
Vent Area
in Sq. Feet
SV-A-10
21
42
10
0.07
SV-A-20
42
84
20
0.14
SV-A-30
63
126
30
0.21
SV-A-40
84
168
40
0.28