Gutter Downspout Calculator
Gutter Downspout
Size gutters and downspouts for your roof.
Formula
Flow Rate = Roof Area x Rainfall x 0.0104
Frequently Asked Questions
How many downspouts do I need?
One downspout per 600 square feet of roof area is typical.
What gutter size is most common?
5-inch K-style gutters are the most common for residential use.