Gutter Sizing Calculator
Slightly steeper roofs shed water faster, requiring larger gutters. Estimate standard 5-inch vs. 6-inch gutter size requirements for your roof slope.
Recommended Gutter Size
Downspouts: 2" x 3" standard
Standard Gutter Sizes Explained
Gutters protect a home's foundation, siding, and fascia from rot and erosion. Most residential homes use seamless gutters sized at either **5 inches or 6 inches** in diameter. Choosing the right size ensures gutters don't overflow during sudden heavy storms.
Why Pitch & Rain Matter
A gutter's capacity isn't just about the physical width of the house. Steeper roofs slide rainwater down into the gutter faster, increasing the momentary volume surge. Similarly, regions subject to torrential downpours (like the Southeast US) require larger gutter sizes than dry Western states, even for houses of the exact same size.
Downspout Capacity Guidelines
Gutters are only as good as the downspouts draining them. Standard sizing requires **one downspout for every 30 to 40 linear feet** of gutter run:
- 2" x 3" Downspout: Standard residential size. Drains up to **600 square feet** of adjusted roof area.
- 3" x 4" Downspout: Oversized residential. Drains up to **1,200 square feet** of adjusted roof area (required for 6-inch gutters).