Net Free Area (NFA) Calculator

Calculate total NFA from various vent types and quantities.

Linear measurement in the specified unit.
ft
Enter the ridge nfa per foot value for this calculation.
sq in
Number of items or instances.
Enter the soffit nfa each value for this calculation.
sq in

Results

Total Exhaust NFA:
Sum of all calculated values.
-sq in
Total Intake NFA:
Sum of all calculated values.
-sq in
Intake/Exhaust Ratio:
Calculated ratio between values.
-
Reference: Industry Standards. Balanced ventilation per NRCA and FHA guidelines.