Rain Gutter Slope Calculator

The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website.

Rain gutter slope calculator.

2 count the number of downspouts drain pipes on your house building and enter the number in downspouts field. Calculate the gutter slope by dividing the length of the gutter needed by 10. How to use the calculator 1 measure the length of your gutters along the eaves of your roof and plug in the number in the length field. Working out gutter slope as a general rule gutter slope is set at 1 4 inch per 10 feet of guttering.

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. For example if you have 30 feet of guttering the calculation is 1 4 x 3 0 75 i e. The capacity of a sloped rectangular gutter may be approximated by using a gutter cross section area not less than that of a semicircular gutter and a depth to width ratio of at least 0 75. This calculator uses current data to calculate the required size of gutter as well as number and size of downspouts based on your input.

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 hand prior to ordering or installing your gutter system. This means the downspout end of the gutter should be set 3 4 of an inch lower than the other end. Place the line spirit level on the string. If the length of the gutter is 10 5 metres 35 feet the amount of slope required is 1 25 cm 1 4 inch multiplied by 1 metres 3 5 feet which when rounded up is 2 5 cm 1 inch.