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Soffit & Ridge Vent Balance Calculator

Split the required NFA 50/50 between intake and exhaust.

Split the required attic ventilation area 50/50 between intake (soffit) and exhaust (ridge) and convert each half to linear feet of standard vent product (4" continuous soffit ≈ 9 NFI / ft; ridge vent ≈ 18 NFI / ft).

Marcus Laurent By Marcus Laurent
Published Last reviewed 1 min read

Inputs

in²
in²/ft
in²/ft

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Each side = required_NFA_in² / 2. Convert by NFI per ft of product.

In depth

Split the required attic ventilation area 50/50 between intake (soffit) and exhaust (ridge) and convert each half to linear feet of standard vent product (4" continuous soffit ≈ 9 NFI / ft; ridge vent ≈ 18 NFI / ft).