This depends on the size of the roof area & how much water the gutter is handling, but a rule of thumb is no more than 30 ft to a downspout with a 5” gutter, & no more than 40 ft to a downspout with a 6” gutter. We recommend a downspout on each end of the run of gutter if the gutter is longer than this or if your roof area is larger than normal.