Attic Vent NFA Calculator

You're on a roof, the inspector wants to know if you have enough vent area, and you need the number now. Not later, not after you find service to load a website.

Attic Vent NFA Calculator does the math for IRC Section R806.2. Enter your attic floor area, pick your code ratio (1:150 or 1:300) and intake/exhaust split (50/50 or 60/40), and get your answer.

WHAT YOU GET
- Total NFA (net free area) in square inches
- Intake NFA and exhaust NFA, split the way you chose
- How many standard soffit vents you need (based on 8x16 vents at 50 sq in each)
- How many linear feet of ridge vent you need (based on standard 18 sq in/ft)

QUICK REFERENCE A built-in reference card with three sections:
-NFA lookup table for common attic sizes (500 to 3,000 sq ft) at both ratios
-When to use 1:150 vs 1:300, including the climate zone conditions from IRC R806.2
- NFA ratings for 10 common vent types (ridge, soffit, gable, roof louver, turbine)

BUILT FOR CONTRACTORS
- Results are large, scannable numbers. No charts, no graphs, no clutter.
- Smart defaults on every field. Open the app, see a result, change one number.
- Works offline. No internet connection needed, ever.
- No account, no login, no tracking.
- Works with VoiceOver and Dynamic Type.
- No ads, no subscription.

$3.99, once. You own it.