Gutter Calculator

Gutter runs

Enter each separate gutter run and the footprint (plan) area of roof that drains into it. Leave unused runs at 0.

Run 1 (e.g. front eave) — eave length (ft)

Run 1 (e.g. front eave) — roof area draining to it (sq ft)

Run 2 (e.g. back eave) — eave length (ft)

Run 2 (e.g. back eave) — roof area draining to it (sq ft)

Run 3 — eave length (ft)

Run 3 — roof area draining to it (sq ft)

Run 4 — eave length (ft)

Run 4 — roof area draining to it (sq ft)

Roof and rainfall

Roof pitch (/12)

Maximum rainfall intensity (in/hr)

Hanger spacing (in)

Downspout size

Roof area is the flat footprint, not the sloped surface — the pitch factor accounts for slope. Rainfall intensity is your area's design storm in inches per hour (see the rainfall section below).

Results

80 ft of 5" K-style gutter with 2 2x3 downspouts, 42 hangers, and 4 end caps.

Recommended gutter size

5" K-style

A 5" K-style gutter handles every run, with about 40% capacity to spare on the busiest one.

Five-inch is the standard residential size, so parts and colors will be easy to find.

Gutter length: 80 linear ft

Downspouts / outlets: 2 / 2

Hangers: 42

End caps (straight runs): 4

Roof pitch factor: 1.1

Run 1 adjusted area: 3,300 sq ft → 5", 1 downspout

Run 2 adjusted area: 3,300 sq ft → 5", 1 downspout