Rain Gutter Slope Calculator

Working out gutter slope as a general rule gutter slope is set at 1 4 inch per 10 feet of guttering.

Rain gutter slope 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. To limit the effects of thermal expansion in gutters 50 ft. 15 m is a practical maximum gutter length to be served by a downspout. 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.

Place the line spirit level on the string. Calculate the gutter slope by dividing the length of the gutter needed by 10. 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. 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.

The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. For example if you have 30 feet of guttering the calculation is 1 4 x 3 0 75 i e. 2 count the number of downspouts drain pipes on your house building and enter the number in downspouts field. 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.