Gutter Downspout Size Calculator

2 4 gutter and downspout sizing and location calculations both metric and english units.

Gutter downspout size calculator.

Downspout sizing in sizing downspouts the following considerations apply. 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. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. This calculator uses the equations that are laid out in the smacna handbook.

Doubling the number of downspouts halves the required capacity for each. 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. Gutter professionals have experience matching the gutters and the downspouts. Remember to save this spreadsheet to your own computer.

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. Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist. Size downspouts to fit the gutter. Now that we are well aware of the various gutter downspout sizes and styles let us dig deeper into the materials used for effective downspouts and how much they shall cost.

The second most common style of downspouts in urban homes is the rectangular downspout coming under a range of sizes such as 2 3 3 4 and 4 5. We will use the larger of the two or 310 sq ft for our first calculation. Downspouts should be constructed with conductor. Water pipe size calculator information video water pipe size calculators size every pipe in your project in seconds with just 3 clicks.

This calculator serves as an information source only. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Downspout sizes are based on table 1 3 dimensions of standard downspouts page 1 4 of the architectural sheet metal manual 7th edition. The size of the downspout should be constant through out its length.

The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. Metal era recommends that you verify all data obtained. First we will find the maximum amount of rain that will be captured in gallons per minute. 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.

3 more clicks will get a pump size if req d.