Gutter Downspout Size Calculator

We recommend using this calculator as a basic tool to begin determining the requirements for your drainage system however all information should be verified by.

Gutter downspout size calculator. Start pressure length to the worst case and height difference. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. The size of the downspout should be constant through out its length. This calculator serves as an information source only.

Downspouts should be constructed with conductor. Downspouts of less than 7 00 sq in 4515 sq mm cross section should not be used except for small areas such as porches and canopies. As far as downspouts go they run at 2 x3 and 3 x4 in size or 3 or 4 inches in diameter. This calculator uses the equations that are laid out in the smacna handbook.

Water pipe size calculator information video water pipe size calculators size every pipe in your project in seconds with just 3 clicks. 2 4 gutter and downspout sizing and location calculations both metric and english units. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. 3 more clicks will get a pump size if req d.

Doubling the number of downspouts halves the required capacity for each. Northclad gutter size requirement calculator this calculator uses current data to calculate the required size of gutter as well as number and size of downspouts based on your input. Gutter professionals have experience matching the gutters and the downspouts. First we will find the maximum amount of rain that will be captured in gallons per minute.

Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist. Downspout sizing in sizing downspouts the following considerations apply. For example a 6 inch k style gutter requires a 3 x 4 downspout while a 5 inch k style gutter uses a 2 x 3 downspout. The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website.

Remember to save this spreadsheet to your own computer. Metal era recommends that you verify all data obtained. Downspout sizes are based on table 1 3 dimensions of standard downspouts page 1 4 of the architectural sheet metal manual 7th edition. We will use the larger of the two or 310 sq ft for our first calculation.

Now architects engineers designers and contractors can easily and accurately size downspouts and gutters according to the specifications in smacna s architectural sheet metal manual 7th edition 2012.