Gutter LF and Downspout Count Takeoff
Gutter footage, downspout count, pipe, and hangers.
Example
You enter
- Total eave / gutter length (ft) 140
- Tributary roof area (ft²) 2400
- Max area per downspout (ft²) 800
- Downspout drop height (ft) 10
- Gutter hanger spacing (ft) 2
You get
- Gutter footage 140 LF
- Downspouts 3
- Downspout pipe (LF) 30
- Gutter hangers 70
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Scopegutter = eave; downspouts = ceil(roof area / max area per downspout); pipe = downspouts x wall height; hangers = ceil(eave / spacing). 140 LF of eave on a 2,400 sf roof at 800 sf per downspout is 3 downspouts, 30 LF of downspout pipe, and about 70 hangers; a bigger 4,000 sf roof needs 5 downspouts and 50 LF of pipe. The roof area drives the downspouts, the eave drives the gutter and hangers. Distinct from the gutter and downspout cross-section sizing.
Formula or tablegutter_lf = eave_length_ft; downspouts = ceil(roof_area_sf / max_area_per_downspout_sf); downspout_pipe_lf = downspouts x wall_height_ft; hangers = ceil(eave_length_ft / hanger_spacing_ft).
Source and editionGutter takeoff identity by name (gutter runs the eave; downspouts from the roof area over the per-downspout area; pipe and hangers from height and spacing); first-principles arithmetic.
Free accessThe takeoff arithmetic is public first-principles; the drainage area per downspout comes from the gutter and downspout size and the rainfall.
What governsEstimate. AHJ and licensed professional govern.
API field nameseave_length_ft, roof_area_sf, max_area_per_downspout_sf, wall_height_ft, hanger_spacing_ft, gutter_lf, downspouts, downspout_pipe_lf, hangers
- Area per downspout ~800 sf per downspout default; the downspout size and rainfall govern (from gutter-downspout)SMACNA / gutter-downspout
- Hanger spacing ~2 ft on center (tighter in snow country)installation practice