Gutter Calculator
Enter your roof's gutter line. We'll size the linear feet plus all the connectors, downspouts, and end caps you need.
Advanced options
- Outside corners
- 0
- Inside corners
- 0
- End caps
- 0
- Downspouts
- 0
- Downspout extensions (3 ft / 0.9 m)
- 0
- Gutter hangers
- 0
- Estimated cost
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How the gutter calculator works
A typical house with 120 linear feet of gutter needs 4 downspouts, 60 hidden hangers, 2 outside corners, and 2 end caps. Downspouts go in at one per 35 feet of run, hangers at 24 inches on center, and 5-inch K-style aluminum handles the drainage for most residential roofs. Add one 3-ft downspout extension per downspout to carry water away from the foundation.
Gutter runs linear feet along your roof eaves. Add an outside corner for each external (90° outward) turn, an inside corner for each internal (90° inward) turn. End caps cap the open ends of any gutter run that doesn't dump into a downspout or another section.
Downspout sizing
Rule of thumb: 1 downspout per 35–40 linear feet of gutter (1 per 10–12 m). For roofs over 1,500 sq ft (140 m²) of drainage area, bump to 1 per 25 ft. Heavy rain regions (Pacific Northwest, Gulf Coast) bump to 1 per 25 ft regardless.
Gutter size by roof
- 5" K-style — handles up to ~1,400 sq ft (130 m²) of roof drainage area per downspout. Standard for most US residential.
- 6" K-style — handles up to ~2,400 sq ft (220 m²). Use for steep pitches (8:12+), heavy-rain regions, or large roof planes.
- 6" half-round — same capacity as 6" K-style but premium aesthetic for traditional or historic homes.
Hangers and brackets
Modern gutters use hidden hangers — internal brackets screwed up into the fascia through the inside back of the gutter. Space at 24" (60 cm) OC; closer in heavy snow regions or on long unsupported runs.
Common questions
Seamless or sectional?
Seamless gutters are formed on-site by a roll-forming machine that cuts to length — no joints except at corners and downspouts. Way fewer leak points; ~30% more expensive. Sectional ("box store") gutter comes in 10-ft sections you connect with sealant. Either works; seamless is the better long-term choice for a primary residence.
What about gutter guards?
Gutter guards (mesh, foam, surface-tension covers) reduce cleanings from twice-yearly to once or once-every-few-years. Mesh inserts ($1–$3/ft) work well for most leaves. Surface-tension covers (Gutter Helmet, LeafGuard) work for pine needles but cost $20–$40/ft installed. Fine if you have lots of trees; overkill if you don't.
How much does gutter installation cost?
5" aluminum K-style installed: $5–$12/linear ft. Copper or zinc seamless: $20–$40/linear ft. Plus $50–$100 per downspout, plus $25–$50 per corner. A typical 1,500 sq ft house with ~120 ft of gutter: $750–$2,500 for aluminum, $3,000–$5,000+ for premium materials.
For the roof above the gutters, see the roof area calculator or shingles calculator.
Planning the full project?
These calculators usually get run in the same afternoon.