Ridge Vent Length
Calculate ridge vent length with clear inputs, formula guidance, and practical result checks.
Ridge Vent Length measurements
Enter your values, then calculate.
Result
How to calculate ridge vent length
This calculator finds required ridge vent length based on attic floor area, a code-based ventilation ratio, and the vent product's net free area per foot.
How the calculation works
Ridge vent length = (Attic area ÷ Ventilation ratio) × 144 ÷ Net free area per foot. This converts the required ventilation area (in square feet) to square inches, then divides by the vent's rated net free area per linear foot.
Example
1,600 sq ft attic area, a 1:150 ventilation ratio, and a vent product rated at 18 sq in NFA per foot: (1,600÷150)×144÷18 = 10.67×144÷18 ≈ 85.3 ft.
Frequently asked questions
How is Result calculated?
Result = [Attic floor area] ÷ [Vent ratio] × 144 ÷ [Net free area per foot].
Is the Ridge Vent Length free to use?
Yes — every calculator on Simple Calculator Tools is free, runs in your browser, and does not require an account.
Ridge Vent Length
Ridge vent length = (Attic area ÷ Ventilation ratio) × 144 ÷ Net free area per foot. This converts the required ventilation area (in square feet) to square inches, then divides by the vent's rated net free area per linear foot.
Let's understand your ridge vent length result.
Calculate a result above and this guide will help you interpret it using this calculator's own formula and explanation.
Pro Tips for Ridge Vent Length
- A balanced ventilation system typically splits required net free area between ridge (exhaust) and soffit (intake) vents — confirm your specific design's split.
- Net free area per foot varies significantly by ridge vent product — use the manufacturer's specific rated NFA, not a generic assumption.
Common Ridge Vent Length Mistakes to Avoid
- Using a generic net free area assumption instead of the specific ridge vent product's manufacturer-rated NFA, which varies meaningfully between products.
When to Use This Calculator
This calculator finds required ridge vent length based on attic floor area, a code-based ventilation ratio, and the vent product's net free area per foot.