✓ SMACNA Architectural Sheet Metal Standard
Gutter Sizing & Downspout Calculator
Determine whether you need 5" or 6" K-style gutters, number of downspouts, and hidden hangers based on roof area.
Roof Drainage Area & Eaves
Gutter System Specifications
Recommended Size 6-Inch K-Style Seamless
Downspouts 4 Drops 3" × 4" Oversized
Hidden Fascia Hangers (24" spacing): 61 Hangers
Inside / Outside Corners (Miters): 4 Corners (typical)
Total Gutter Trough Length: 120 Linear Ft
Frequently Asked Questions
Should I install 5-inch or 6-inch gutters?
Standard 5-inch K-style gutters can handle drainage for roof sections up to 5,500 square feet. 6-inch gutters hold 40% more water and are strongly recommended for steep pitch roofs (where water rushes down fast), metal roofs, or rainy geographic areas.
How many downspouts do I need per foot of gutter?
The building code standard is at least one standard downspout (2"×3" or 3"×4") for every 30 to 40 linear feet of gutter run to prevent overflowing during heavy downpours.
What is the correct slope for rain gutters?
Gutters must be sloped toward the downspouts at a minimum rate of 1/4 inch per 10 feet of horizontal run (or 1/2 inch per 20 feet) to ensure standing water does not pool and breed mosquitoes.