Ridge Vent Calculator
Estimate ridge-vent length from attic area, an editable ventilation ratio, exhaust share, product net-free-area rating and package length.
Default project preview
24 ft
Total modeled net free area
864 in²
Exhaust net free area
432 in²
Order length
25.9 ft
Vent packages
2
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Attic floor area
Enter this project assumption in ft². The current imperial default is 1800 ft².
Ventilation ratio denominator
Enter this project assumption in 1 :. The current imperial default is 300 1 :.
Exhaust share of total vent area
Enter this project assumption in %. The current imperial default is 50 %. Minimum: 1. Maximum: 100.
Ridge vent net free area
Enter this project assumption in in²/ft. The current imperial default is 18 in²/ft.
Available ridge length
Enter this project assumption in ft. The current imperial default is 60 ft. Minimum: 0.
Cuts and end allowance
Enter this project assumption in %. The current imperial default is 8 %. Minimum: 0. Maximum: 50.
Vent length per package
Enter this project assumption in ft. The current imperial default is 20 ft.
Price per package
Enter this project assumption in a unitless value. The current imperial default is 58. Minimum: 0.
How to read the outputs
Total modeled net free area
1:300 entered ratio. Default preview: 864 in².
Exhaust net free area
50% exhaust share. Default preview: 432 in².
Order length
includes cuts and ends. Default preview: 25.9 ft.
Vent packages
20 ft each. Default preview: 2.
Purchased length
full packages. Default preview: 40 ft.
Material cost
ridge vent only. Default preview: $116.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Total net free area = attic area ÷ entered ratio. Multiply by exhaust share, divide by ridge-vent NFA per length and add waste.
BuildMeter Guides
Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
Ridge Vent Calculator questions
Why is intake ventilation important?+
Ridge exhaust cannot perform as intended without a clear intake path, commonly at soffits or low roof areas.
Is nominal vent width useful?+
Use the published net free area rating, not visible vent dimensions.
Can ridge vent be used on every roof?+
No. Ridge geometry, roof assembly, weather exposure and manufacturer requirements determine suitability.