Gutter + Downspout Calculator
Seamless K-style gutter + downspout takeoff with drainage-area sizing rules, corner + end-cap count, and optional leaf-guard.
Aluminum K-5: ~$3.50. K-6: ~$4.50.
One at each open end
One per 40 LF of gutter
12 for 1-story; 22 for 2-story
0 for none
25–40 LF/hr for 2-person crew
Result
- Gutter cost
- $560
- Corners
- $72
- End caps
- $24
- Downspouts
- $144
- Elbows
- $60
- Leaf guards
- —
- Material subtotal
- $860
- Labor
- 6.9 hr · $381
- Total installed
- $1,241
- Effective $ / LF
- $8
This estimate is based on national average costs and may vary by region, project specifics, and market conditions. Use as a starting point for your bids.
Sizing gutters by drainage area
The IRC rule: 1 sq in of downspout cross-section per 100 sq ft of roof drainage area at 1-in/hr rainfall. Translates to:
- 5-in K-style (5.5 sq in): handles ~550 sq ft per downspout
- 6-in K-style (10 sq in): handles ~1,000 sq ft per downspout
- 2 × 3-in downspout (6 sq in): up to 600 sq ft of roof
- 3 × 4-in downspout (12 sq in): up to 1,200 sq ft of roof
In high-rainfall regions (Gulf Coast, Pacific Northwest) size up — what handles 1-in/hr won't handle the 3-in/hr storms those regions get a few times a year.
Installed pricing benchmarks
| System | Installed $/LF |
|---|---|
| Seamless K-5 aluminum | $6–11 |
| Seamless K-6 aluminum | $8–14 |
| Half-round copper | $25–45 |
| European box copper | $30–60 |
| Leaf guards (micro-mesh) | +$20–30 |
| Leaf guards (foam / screen) | +$6–12 |
Add 20–30% for 2-story work. Add $50–100 per drop for splash blocks, drain extensions, or French-drain connections at the discharge end.
Layout rules
- One downspout per 40 LF of gutter run (minimum)
- End caps required at every open end
- Outside corners (90° away from house) AND inside corners (90° into a recess) priced separately
- 1/4 in slope per 10 ft toward each downspout
- 3 elbows per downspout: 2 at top + 1 kick-out at bottom
Frequently asked questions
How many downspouts do I need?
One downspout per 40 LF of gutter run as the residential minimum. Bump to one per 30 LF for heavy-rain regions or wide-eave 2-story homes. The IRC drainage rule: 1 sq in of downspout for every 100 sq ft of roof drainage area at 1-in/hr rainfall. A 2 × 3-in downspout (6 sq in) handles 600 sq ft; 3 × 4-in (12 sq in) handles 1,200 sq ft.
5-in vs 6-in K-style — when do I size up?
5-in K-style (5.5 sq in cross-section) handles up to ~600 sq ft of roof drainage per downspout at 1-in/hr rain. 6-in K-style (10 sq in) handles ~1,200 sq ft. Step up if you're in a heavy-rain region (Gulf Coast, Pacific Northwest), have a 2-story house with wide eaves, or have a complex roof that channels multiple valleys into one downspout location.
Seamless vs sectional gutters?
Seamless (formed on-site from a coil) is the modern residential standard — fewer leak points, cleaner aesthetic, ~$2 more per LF than sectional. Sectional gutters (10 ft pre-cut sections from a home center) have leak-prone joints every 10 ft but are the only DIY option. Pros install seamless almost exclusively; the $200 cost difference on a typical home doesn't justify the lifetime headache of seam leaks.
Do leaf guards work?
Yes, with caveats. Micro-mesh systems (Gutterglove, LeafFilter style) keep out pine needles and debris but cost $20–30 per LF installed — often more than the gutters themselves. Curved-screen and foam inserts are cheaper ($6–12/LF) but accept more debris. They reduce cleaning frequency but don't eliminate it. Customers asking 'will I never need to clean my gutters again' want a different answer than the truth.
What's installed gutter pricing?
Seamless aluminum K-5: $6–11 per LF installed. K-6 aluminum: $8–14 per LF. Half-round copper: $25–45 per LF (premium aesthetic + 50+ year life). European box copper: $30–60 per LF. Downspouts at $4–8 per LF aluminum, $20–40 per LF copper. Leaf guards add $6–25 per LF depending on system. Two-story work adds 20–30% for ladder time.
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