Gutter Size Calculator
Calculate the proper gutter size for your home based on roof area, rainfall intensity, and roof pitch. Ensure proper drainage and prevent water damage.
Step 1: Roof Specifications
Gutter Sizing Formula
Gutter Size (inches) = (Roof Area × Rainfall Intensity × Pitch Factor) ÷ (Downspouts × 100)
Standard gutter sizes: 5″, 6″, 7″ K-style or half-round
Step 2: Climate & Options
Common Gutter Sizes
Small roofs: 5″ gutters (up to 1,500 sq ft)
Medium roofs: 6″ gutters (1,500-3,500 sq ft)
Large roofs: 7″ gutters (3,500-5,000+ sq ft)
Commercial: 8″+ gutters
Gutter Size Results
Recommended Gutter Size
Gutter Type Comparison
| Gutter Type | Capacity | Best For | Common Sizes |
|---|
Gutter Sizing Formula
Gutter Size = (Roof Area × Rainfall Intensity × Pitch Factor) ÷ (Downspouts × 100)
Where:
• Roof Area = Total roof surface area (square feet)
• Rainfall Intensity = Maximum rainfall rate (inches per hour)
• Pitch Factor = Multiplier based on roof slope
• Downspouts = Number of drainage points
Standard sizing guidelines:
• 5″ gutters: Up to 1,500 sq ft roof area
• 6″ gutters: 1,500-3,500 sq ft roof area
• 7″ gutters: 3,500-5,000+ sq ft roof area
Example Calculation
Example: 2,000 sq ft Home
Roof Area: 2,000 sq ft
Rainfall Intensity: 4 in/hr
Roof Pitch: Medium (factor 1.1)
Downspouts: 3
Calculation:
(2,000 × 4 × 1.1) ÷ (3 × 100) =
8,800 ÷ 300 = 29.33
√29.33 ≈ 5.4″ → Rounded to 6″ gutter
Result: 6″ K-style gutters with 3 downspouts
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