Enter your ridge length, roof pitch, and vent width into the calculator to determine the net free area.

Ridge Vent Calculation Formula

The following formula is used to calculate the net free area for ridge vents.

Net Free Area = Ridge Length (ft) * Vent Width (in) * (Roof Pitch / 12)

Variables:

  • Net Free Area is the effective area for ventilation (sq in)
  • Ridge Length is the length of the ridge vent (ft)
  • Vent Width is the width of the vent (in)
  • Roof Pitch is the slope of the roof

To calculate the net free area, multiply the ridge length by the vent width and adjust for the roof pitch.

What is Ridge Vent Calculation?

Ridge vent calculation involves determining the necessary net free area to provide adequate ventilation for your roof. This process helps in ensuring proper air circulation within the attic, preventing moisture buildup and reducing cooling costs.

How to Calculate Net Free Area?

The following steps outline how to calculate the net free area using the given formula.


  1. First, measure the ridge length of your roof.
  2. Next, determine the width of the ridge vent you plan to install.
  3. Measure the roof pitch, which