How this calculator works
The calculator adds waste to total gutter run and divides by stock section length for gutter pieces. Downspouts are estimated from total run divided by downspout spacing. Hangers are based on gutter run converted to inches and divided by hanger spacing, plus one end hanger.
Example: 120 feet of gutter run with 10% waste needs 132 feet of gutter, or 14 ten-foot sections. With 40 foot downspout spacing, the estimate is 3 downspouts. With hangers every 24 inches, the estimate is 61 hangers.