Pick your city, type the roof's size seen from above, its shape and pitch, and pick the gutter. You get 5″ or 6″ gutters, how many downspouts and where, and every part to buy — sized by the copper gutter handbook's method for your own rainfall. Switch to What it costs for the price of the same gutters, hung by a pro or by you, with gutter guards or without, or what a cleaning costs.
Your gutters
6″ K-style gutters, 2 downspouts100 ft of gutter · 2×3″ rectangular downspouts · Chicago, IL: 6.8 in/hr, 10-year storm
Quick answer: a 50 × 30 ft house with a gable roof at 6–8/12 in Chicago (6.8 in/hr in a 10-year storm) needs 6″ K-style gutters and 2 downspouts of 2×3″, one at the end of each 50 ft side. Each side then runs 70% full. Choose 5″ gutters instead and you need 4 downspouts. In Seattle (2.1 in/hr) the same house takes 5″ gutters with 2 downspouts. Change the city, the roof or the gutter above and the answer follows.
How to use the gutter size calculator
- Pick the nearest city from the 75 in the list. Or pick my own rainfall and type the 5-minute rain intensity, in inches an hour, from your local code or a rain map.
- Choose the storm: a 10-year storm is the usual choice for a house; a 100-year storm is the safe one.
- Pick the roof: gable (gutters on the two long sides), hip (gutters all round) or shed (one low side). Then type the roof’s length along the gutters and its width front to back, measured from above, eave edge to eave edge. Then pick its pitch: a 6/12 roof rises 6 inches every foot.
- Choose the gutter shape and the downspout: K-style with 2×3″ or 3×4″ rectangular downspouts, or half-round with 3″ or 4″ round ones. Then pick the stories, the hanger spacing and how steeply the gutter falls.
- You get the gutter size, the downspouts per side, how full each gutter runs, and the parts list. Copy link keeps your house.
- Switch to What it costs to price the same gutters. Pick seamless aluminum, aluminum in 10 ft lengths, vinyl, galvanized steel or copper, and whether the old gutters come down first. You get the pro’s price with its middle, every gutter side by side, and the parts if you hang aluminum lengths yourself. Pick a gutter guard to add it, Keep them to price the guards alone on the gutters you have, or Just clean them for a cleaning’s price and the years each guard takes to pay it back.
What new gutters cost
The cost mode prices the gutter the calculator just sized. For the 50 × 30 ft house above, 100 ft of seamless aluminum hung by a pro costs $610–$990 on Homewyse’s national figures (May 2026). Replacing old gutters costs $800–$1,420, about $1,110 in the middle, because taking the old ones down and hauling them away adds $200–$430. Homewyse prices store lengths at $6.40–$7.86 a foot, against $2.77–$3.41 for the coil a seamless installer forms on site.
| Gutter | 100 ft (about a 1,000 sq ft house) | 150 ft | 200 ft |
|---|---|---|---|
| Seamless aluminum | $610–$990 | $890–$1,450 | $1,170–$1,910 |
| Aluminum in 10 ft lengths | $1,020–$1,530 | $1,510–$2,250 | $1,990–$2,970 |
| Vinyl | $290–$400 | $430–$600 | $570–$800 |
| Galvanized steel | $800–$900 | $1,200–$1,350 | $1,600–$1,800 |
| Copper | $2,000–$2,870 | $3,000–$4,310 | $4,000–$5,750 |
| Taking old gutters down (add) | $200–$430 | $270–$610 | $340–$790 |
Where the prices come from: Homewyse prices aluminum line by line (the gutter, the labor, the supplies), read at eight lengths from 20 to 500 ft. This Old House prices vinyl, galvanized steel and copper by the foot in two guides. Vinyl, for example, is $571 for a 200 ft job in one and $4 a foot seamless in the other, and the calculator gives the range between the two. Its average: “Gutter installation costs $600 to $5,800 for a typical 2,000-square-foot home, or $3,200 on average.” No roof measurements? This Old House’s rule: “A quick rule of thumb is to divide your home’s square footage by 10 to estimate the linear feet of gutter you’ll need.”
Hanging them yourself: for the same house, Homewyse’s gutter and supplies come to $700–$860. Add 52 hangers, 4 end caps, 6 elbows and 2 downspout pieces at The Home Depot’s prices (This Old House’s table) for $140–$1,010 more. That makes $850–$1,880. The range is wide because hangers run $2 to $17 each. A taller house costs more to hire out: “Two-story homes are more dangerous to work on and require higher labor rates. Three-story homes may require special equipment like scaffolding or cranes.”
What gutter guards cost
The cost mode prices a guard on the same feet three ways. Yourself: the makers’ own prices for a 5″ or 6″ gutter, in whole packs. By a gutter pro: those guards plus Homewyse’s labor and supplies for “Basic labor to install rain gutter cover with favorable site conditions.” By a guard company: This Old House’s 2026 survey of 1,000 homeowners, $39.71 a foot on average across all kinds, labor in. On the 50 × 30 ft house above, micro-mesh guards on its 6″ gutters cost $610–$670 put on by a gutter pro, against about $4,050 from a guard company. New gutters with micro-mesh guards on them cost $1,410–$2,090 with the old ones taken down.
| Guard | Yourself, 100 ft | By a gutter pro, 100 ft | By a gutter pro, 200 ft | Guard company, 100 / 200 ft |
|---|---|---|---|---|
| Micro-mesh (Raptor, Waterlock) | $440–$470 | $610–$670 | $1,080–$1,240 | $4,050 / $8,100 |
| Screen (A-M) | $150 | $320–$350 | $600–$670 | $3,810 / $7,620 |
| Reverse-curve | — | — | — | $4,120 / $8,240 |
| Foam (GutterFoam) | $440–$500 | $600–$710 | $1,030–$1,200 | $2,160 / $4,320 |
| Brush (GutterBrush) | $500 | $670–$700 | $1,210–$1,270 | $1,890 / $3,790 |
A 5″ gutter takes cheaper packs: 100 ft of micro-mesh is $420–$430 to buy, foam $280–$380 and brush $350. No store sells a reverse-curve guard: “Unlike most other guard types, they require professional installation and can last up to 20 years with minimal upkeep.” And on old gutters: “If your current gutters are in bad shape, installers typically recommend installing new ones before adding guards.”
In a downpour the makers and This Old House do not always agree. GutterFoam: “The filter is non-absorbent so it allows large volumes of water to flow right through.” This Old House: “Foam gutter guards work well in moderate rain conditions, but they struggle during heavy downpours.” Raptor’s micro-mesh passed its test: “The Raptor guard also filters water well, even during our simulated downpour test.”
What gutter cleaning costs
Pick Just clean them under Old gutters. This Old House prices a cleaning by the foot, more a foot on a taller house (“The cost data featured in this guide is based on pricing from 2026 estimates from Angi.”). The 100 ft of the house above costs $100–$130 a cleaning on one story, never under the guide’s $100, so $200–$250 a year at two cleanings: “You should have your gutters cleaned twice per year. You’ll only need to clean them once every year or so if you have gutter guards.”
| Stories | A foot | A typical house | 100 ft | 200 ft |
|---|---|---|---|---|
| 1 | $0.95–$1.25 | $100–$250 | $100–$130 | $190–$250 |
| 2 | $1.00–$1.85 | $180–$360 | $100–$190 | $200–$370 |
| 3 | $1.25–$2.25 | $210–$450 | $130–$230 | $250–$450 |
A guard saves about one cleaning a year, so its price in cleanings is its payback in years. On the one-story house, micro-mesh put on by a gutter pro ($610–$670) is about 6 cleanings: 6 years. From a guard company ($4,050) it is 36 years, brush from a guard company ($1,890) 17. This Old House still finds guards worth it under trees: “this upfront expense often pays off in reduced cleaning needs—especially for homes in areas with dense tree cover or high local labor costs.”
How gutters are sized
The calculator follows the Copper Development Association’s design handbook (the SMACNA method), with gutter capacities from This Old House. Four steps:
- The rain. A gutter has to carry the hardest burst, not the day’s total: “Rainfall intensity is measured over a 5-minute period.” The handbook’s table lists two storms for each city: “These sections represent the intensities which are likely to be exceeded once in 10 years, and once in 100 years, respectively.” Chicago’s 10-year storm is 6.8 inches an hour; its 100-year storm is 9.3.
- The roof each gutter drains. The handbook measures the roof as seen from above and adds a little for the pitch: “The plan roof area should be multiplied by this factor.” It does not use the roof’s true sloped area, because “using the true area in the calculations has typically resulted in oversized gutters, downspouts and drains.” A 50 × 30 ft gable is 1,500 sq ft from above. Each long side drains half of it, 750 sq ft, and at 6–8/12 that is 750 × 1.10 = 825 sq ft.
- The downspouts. “It is based on the assumption that during a rainfall with an intensity of 1 inch per hour, each square inch of downspout can drain 1200 square feet of roof.” A 2×3″ downspout is 6 square inches, so it drains 7,200 sq ft at 1 in/hr. In Chicago that becomes 7,200 ÷ 6.8 = 1,059 sq ft, more than the 825 sq ft each side sends it. And “Each downspout should drain a maximum of 50 feet of gutter.”
- The gutter. Fine Homebuilding: “Divide your favored gutter’s 1-in.-per-hour watershed (see the chart below) by the five-minute rainfall intensity (from the map above). This determines the maximum watershed level gutters can serve between downspouts.” A 5″ K-style gutter is rated at 5,520 sq ft, so it can carry 5,520 ÷ 6.8 = 812 sq ft in Chicago. Each side sends 825, so 5″ is too small with one downspout a side. A 6″ gutter carries 7,960 ÷ 6.8 = 1,171 sq ft, so each side runs 70% full. Or keep the 5″ gutter and add downspouts: “Going from one downspout to two doubles the watershed that a section of gutter can drain.”
Gutter, downspout and pitch numbers
| Gutter or downspout | Roof it drains at 1 in/hr | In Chicago (6.8 in/hr) |
|---|---|---|
| 5″ K-style gutter | 5,520 sq ft | 812 sq ft |
| 6″ K-style gutter | 7,960 sq ft | 1,171 sq ft |
| 5″ half-round gutter | 2,500 sq ft | 368 sq ft |
| 6″ half-round gutter | 3,840 sq ft | 565 sq ft |
| 2×3″ downspout (6.00 sq in) | 7,200 sq ft | 1,059 sq ft |
| 3×4″ downspout (12.00 sq in) | 14,400 sq ft | 2,118 sq ft |
| 3″ round downspout (7.07 sq in) | 8,484 sq ft | 1,248 sq ft |
| 4″ round downspout (12.57 sq in) | 15,084 sq ft | 2,218 sq ft |
| Roof pitch | Factor |
|---|---|
| Flat up to 3/12 | 1.00 |
| 4/12 to 5/12 | 1.05 |
| 6/12 to 8/12 | 1.10 |
| 9/12 to 11/12 | 1.20 |
| 12/12 and steeper | 1.30 |
This Old House’s rough rule, “A 2-by-3-inch rectangular downspout can handle about 600 square feet of drainage area, while a 3-by-4-inch downspout can manage up to 1,200 square feet.”, is the handbook’s rule in a storm of 12 inches an hour (7,200 ÷ 12 = 600). The calculator uses your city’s own figure.
Worked examples
- Seattle, the same 50 × 30 ft gable: 2.1 in/hr, so a 5″ K-style gutter carries 5,520 ÷ 2.1 = 2,629 sq ft. Each side’s 825 sq ft fills it only 31%, so 5″ gutters and 2 downspouts.
- Chicago, a 50 × 30 ft hip roof: 160 ft of gutter on four sides. Each long side drains a trapezoid of 525 sq ft (578 at 6–8/12), and each end a triangle of 225 (248). That is less per side than the gable, so 5″ gutters with a downspout on each side: 4 downspouts, 4 corners and no end caps.
- Houston, a two-story 40 × 28 ft gable at 4–5/12: 8.2 in/hr. Each side drains 560 × 1.05 = 588 sq ft, and a 5″ gutter carries 673 there. So 5″ gutters, 2 downspouts, each side 87% full, and two 10 ft pieces of downspout pipe per corner for the 19 ft wall.
- Atlanta, a 60 × 36 ft gable at 9–11/12 with half-round gutters: 7.3 in/hr. Each side drains 1,080 × 1.20 = 1,296 sq ft, and a 6″ half-round carries 526. That takes 3 round downspouts a side (6 in all), each 82% full. With 5″ half-round gutters it takes 8.
- Chicago, the default house sized for a 100-year storm: 9.3 in/hr. One 2×3″ downspout now drains only 774 sq ft, less than a side’s 825, so each side needs 2 downspouts. With 2 a side the 5″ gutter is enough: 5″ gutters and 4 downspouts.
Slope, hangers and downspout pipe
The gutter falls toward each downspout. This Old House: “Standard gutters are typically sloped about 1/4 inch for every 10 feet.” With one downspout on a 50 ft side the gutter falls 1¼″. With two, it is highest in the middle and falls 5/8″ to each end. A steeper fall carries more water: “Pitch your gutters by 1/8 in. per ft., and you can multiply the watershed by 1.4.” The ⅛″ a foot option uses that, and it can turn a 6″ answer into a 5″ one. It does need room under the drip edge: 6¼″ of fall on a 50 ft run.
Hangers: the handbook says “spaced a maximum of 30″ O.C. in snow areas, or 36″ O.C. in non-snow areas”, Gutterall 18 inches in heavy rain or snow. The calculator counts a hanger every 24 inches unless you pick 36 or 18. Downspout pipe comes in 10 ft pieces. The calculator takes 10 ft for the first story and 9 ft for each story above it. New York State’s specification says “Install a minimum of 2 straps at each downspout section.”
Common mistakes
- Sizing for the whole roof. Each gutter run only carries the part of the roof that drains into it. A gable sends half its roof to each side.
- Using the sloped roof area. The handbook uses the area seen from above times a small pitch factor. The sloped area oversizes everything.
- Too few downspouts. Adding a downspout is usually cheaper than a bigger gutter. And “Avoid locations where water must flow around a corner to reach a downspout.”
- Undersized downspouts. “Downspouts should have a cross-sectional area of at least 7 square inches, except for small areas such as porches and canopies.” A 2×3″ downspout is 6, which is why many installers fit 3×4″ on 6″ gutters.
- Long runs to one outlet. This Old House: “gutters that run 60 feet or longer should have at least two outlets”. The handbook’s limit is 50 ft of gutter per downspout.
Questions
Do I need 5 or 6 inch gutters?
It depends on your rain and how much roof each gutter drains. A 5″ K-style gutter carries 5,520 sq ft of roof at 1 in/hr; divide by your city’s 5-minute intensity. In Chicago that is 812 sq ft per downspout, in Seattle 2,629. When a side sends more than that, use 6″ gutters (7,960 sq ft at 1 in/hr) or add a downspout.
How many downspouts do I need?
At least one for every 50 ft of gutter, and enough that each drains no more than its share. A downspout drains 1,200 sq ft per square inch at 1 in/hr. A 2×3″ downspout is 6 sq in, so 7,200 ÷ your intensity: 1,059 sq ft in Chicago, 3,429 in Seattle.
How much do gutter guards cost?
For 100 ft of 6″ gutter: $150 (screen) to $500 (brush) if you put them on yourself, $320–$710 put on by a gutter pro, and $1,890–$4,120 from a guard company, which charges $18.94 a foot for brush to $41.22 for reverse-curve (This Old House’s 2026 survey).
How much does gutter cleaning cost?
For 100 ft of gutter, $100–$130 on a one-story house, $100–$190 on two stories and $130–$230 on three (This Old House, 2026: $0.95–$2.25 a foot). It averages $275 a visit, from $100 to $450. Twice a year, or once with gutter guards.
How much does it cost to replace gutters?
For 100 ft of seamless aluminum, about $800–$1,420 hung by a pro with the old gutters taken down and hauled away (Homewyse, May 2026). For 200 ft, about $1,510–$2,700. Vinyl costs less and copper costs about three times as much. Switch the calculator to What it costs for your own roof’s feet.
Are seamless gutters cheaper than sectional?
Hung by a pro, on Homewyse’s figures, yes: 100 ft of seamless aluminum is $610–$990 against $1,020–$1,530 for aluminum in 10 ft lengths. The coil a seamless machine forms costs $2.77–$3.41 a foot, store lengths $6.40–$7.86. This Old House calls sectional the cheaper kind, so ask for a quote of each.
Is it cheaper to install gutters yourself?
Not always: 100 ft of aluminum lengths with the hangers, end caps, elbows and downspouts comes to $850–$1,880, against $610–$990 for a pro’s seamless job. It saves the labor on lengths, not on seamless gutter.
Read next
- Rainwater collection system ideas
- Orange brick exterior color schemes
- Modern rustic home exteriors
- Lake house exteriors
Picking the color next? The free gutter color picker tries every color on your house. Puddles below a downspout? The french drain cost calculator prices the fix. Re-siding at the same time? The siding calculator counts the boxes for the same walls. The 2D planner draws the house’s rooms to scale.
Sources, read October 16, 2026: the Copper Development Association’s Copper in Architecture Design Handbook, 10. Gutters and Downspouts (Table 10A’s rain intensities for 75 cities, Table 10C’s pitch factors, the 1,200 sq ft downspout rule, the 50 ft rule), its downspout sizes and hung gutter basics; This Old House, How To Size Gutters and Downspouts (gutter capacities, slope); Fine Homebuilding, Sizing Gutter Systems (Andy Engel); Gutterall’s hanger instructions; New York State Office of General Services, Gutters and Downspouts specification. Prices, read October 18, 2026: Homewyse, Cost to Install Gutters and Cost to Install Seamless Gutters (May 2026, national); This Old House, Gutter Installation Cost (updated October 9, 2026) and Seamless Gutters Cost (updated October 13, 2026). Gutter guards, read October 19, 2026: Homewyse, Cost to Install a Rain Gutter Cover (May 2026); This Old House, Gutter Guard Installation Cost (updated October 12, 2026), Best Gutter Guards of 2026 (updated October 8, 2026), foam and reverse-curve guards; the makers’ own pages: Raptor, A-M, Leafguard, GutterFoam’s FAQ and shop, GutterBrush. Cleaning, read October 19, 2026: This Old House, How Much Does Gutter Cleaning Cost? (updated June 17, 2026). The prices are re-checked every six months. Tucson’s 100-year figure is printed as 19.1 in/hr in the handbook’s table, beside a downspout column that works out to 9.2 (1,200 ÷ 130). Every other row’s two columns agree, so the calculator reads it as a misprint of 9.1. Your local building code has the last word, and this page is re-checked every year.