By The Roofing Brief Team. Last reviewed: October 2026.
Standard gutter dimensions are measured across the top opening: a 5-inch K-style gutter is 5 inches wide, about 3-13/32 inches tall at the front and 3-13/16 inches at the back with a 3-1/4 inch bottom, per DMI’s K-style profile table. A 6-inch K-style is 6 inches wide, 4-1/2 inches at the front, 5 inches at the back and 3-7/8 inches across the bottom. The width label is only one number: a gutter’s full dimensions also include its front and back heights, bottom width, the flat coil it is formed from, its metal thickness, and the cross-section that sets how much water it holds. The tables below give each one, with the maker or code that publishes it, plus the downspout that matches.
What “gutter dimensions” actually measure
Gutter dimensions describe six things, not one: the nominal width (the top opening), the front height, the back height, the bottom width, the coil width the gutter is formed from, and the metal thickness. DMI labels them A (front height), B (top width), C (back height) and D (bottom width) on its profile drawing. The “5-inch” or “6-inch” label refers only to B, measured front to back. Two gutters with the same label can hold different amounts of water because their heights and bottom widths differ by maker: GutterAll lists its 5-inch K-style at about 3-1/2 inches tall with a 3-1/8 inch bottom, close to but not the same as DMI’s.
The number that governs capacity is the cross-section below the front lip, not the labeled width. Treating the K-style profile as a trapezoid from DMI’s dimensions, a 5-inch K-style holds about 14 square inches, or 0.73 gallons per foot, while a 5-inch half-round holds about 9.8 square inches, or 0.51 gallons per foot. Our gutter size chart pairs each width with its capacity and downspout.
Coil width matters for anyone forming seamless, one-piece gutter on site. A roll-forming machine feeds flat aluminum coil and folds it into the profile. Lynch Aluminum’s specification sheet lists 5-inch gutter coil in 0.027 x 11-3/4 in, 0.032 x 11-3/4 in and 0.032 x 11-7/8 in, 6-inch coil at 15 in, and 7-inch coil at 0.032 x 18 in. Englert lists a material width of 11-3/4 to 12-3/8 inches for its 5-inch MetalMan 555 K-style machine, with a maximum of 0.032 inch aluminum, 24 gauge steel or 20 oz copper.
K-style gutter dimensions (the standard residential profile)
K-style gutters, also called ogee gutters, have a flat back, a flat bottom and a decorative front face that mimics crown molding. The front lip sits lower than the back, so water spills forward before it reaches the fascia. The table lists DMI’s published dimensions for each size, the coil width from Lynch Aluminum, and the water held to the front lip.
| Nominal size | Top width (B) | Front height (A) | Back height (C) | Bottom width (D) | Coil width | Held cross-section | Approx. capacity |
|---|---|---|---|---|---|---|---|
| 5-inch K-style | 5 in | 3-13/32 in | 3-13/16 in | 3-1/4 in | 11-3/4 or 11-7/8 in | About 14.1 sq in | About 0.73 gal/ft |
| 6-inch K-style | 6 in | 4-1/2 in | 5 in | 3-7/8 in | 15 in | About 22.2 sq in | About 1.15 gal/ft |
| 7-inch K-style | 7 in | 5-3/8 in | 5-7/8 in | 4-5/8 in | 18 in | About 31.2 sq in | About 1.62 gal/ft |
| 8-inch K-style | 8 in | 6 in | 6-1/8 in | 5-3/8 in | Not listed by Lynch | About 40.1 sq in | About 2.08 gal/ft |
Dimensions: DMI K-style gutter table. Coil widths: Lynch Aluminum specification sheet. Cross-section and gallons per foot are Roofing Brief estimates: the average of top and bottom width times the front height, times 12 inches, divided by 231 cubic inches per gallon. The ogee curve trims a little from that trapezoid, so treat the figures as upper estimates.
The 5-inch K-style is the volume seller; HomeGuide’s gutter installation guide (October 28, 2025) states that most residential homes use 5-inch K-style and that 6-inch adds $1 to $2 per linear foot. By the estimates above, the 6-inch holds about 58% more water per foot than the 5-inch. K&M Sheet Metal’s size chart notes that 5 and 6 inch K-style is roll-formed in lengths up to 40 feet, while 4, 7 and 8 inch sizes are brake-formed in lengths up to 20 feet, which is why the larger sizes are usually special ordered. Our gutter coil guide lists the supplier coil width for 5, 6 and 7 inch gutters.
Half-round gutter dimensions
Half-round gutters are a semicircular trough, the traditional profile on older and higher-end homes and the standard pairing for copper. Because a half circle encloses less area than a K-style of the same width, a half-round holds less water at the same nominal size. The table gives the geometry of a true semicircle and the flow rating the International Plumbing Code, Table 1106.6 (2021), assigns to each size.
| Nominal size | Top opening | Depth | Cross-section area | Approx. capacity | IPC flow rating at 1/8 in per ft |
|---|---|---|---|---|---|
| 4-inch half-round | 4 in | 2 in | About 6.3 sq in | About 0.33 gal/ft | 39 gpm |
| 5-inch half-round | 5 in | 2-1/2 in | About 9.8 sq in | About 0.51 gal/ft | 74 gpm |
| 6-inch half-round | 6 in | 3 in | About 14.1 sq in | About 0.73 gal/ft | 110 gpm |
| 8-inch half-round | 8 in | 4 in | About 25.1 sq in | About 1.31 gal/ft | 247 gpm |
Half-round gutters hang from the fascia on brackets or from the roof on straps rather than nailing flush against the board, so the profile sits slightly forward. That changes the drip-edge and hanger geometry, which is one reason people switching from K-style to half-round should confirm bracket spacing before ordering. Our guide to half-round gutter installation covers hanger spacing and the choice between fascia and roof mounting.
K-style vs half-round: same number, different capacity
A 5-inch K-style and a 5-inch half-round are not interchangeable. From the dimensions above, the K-style holds about 14.1 square inches below its front lip against about 9.8 for the half-round, roughly 43% more water at the same labeled size. A 6-inch half-round, at about 14.1 square inches, holds about the same as a 5-inch K-style. When you match a gutter to a roof, compare cross-section and flow rating, not the nominal width alone.
Shape also drives debris behavior and price. Half-round troughs have no inside corners for leaves to lodge in, and they are the usual profile for copper, which HomeGuide prices at $30 to $50 per linear foot seamless against $6 to $12 for aluminum. For a full breakdown of how the two profiles compare on capacity, cost and house style, see our guide to K-style vs half-round gutters.
Downspout dimensions and how they match the gutter
Downspout dimensions have to keep pace with the gutter above them, or water backs up and overflows at the corners. Rectangular downspouts pair with K-style gutters and round downspouts pair with half-round. IPC Table 1106.3 rates vertical leaders by size; where a common downspout is not listed exactly, the table below shows the nearest listed size.
| Downspout | Cross-section area | IPC Table 1106.3 rating | Typical gutter pairing |
|---|---|---|---|
| 2 x 3 in rectangular | 6 sq in | Near 2-1/2 x 2-1/2 in: 54 gpm | 5-inch K-style, small roofs |
| 3 x 4 in rectangular | 12 sq in | Near 3 x 4-1/4 in: 192 gpm | 5-inch and 6-inch K-style |
| 4 x 5 in rectangular | 20 sq in | 4 x 5 in: 360 gpm | 6-inch and 7-inch K-style, large or commercial |
| 3 in round | About 7.1 sq in | 3 in: 92 gpm | 5-inch half-round |
| 4 in round | About 12.6 sq in | 4 in: 192 gpm | 6-inch half-round |
A 6-inch gutter feeding a single 2 x 3 downspout is a common install mistake: the trough holds about 1.15 gallons per foot but the outlet is only 6 square inches. Step up to a 3 x 4 downspout, or add outlets, when you move to 6-inch gutters. Lynch Aluminum makes 2 x 3 downspouts in 0.019 inch aluminum, 3 x 4 in 0.019 or 0.024 inch, and 4 x 5 in 0.027 inch. Our notes on downspout placement and sizing cover how many you actually need.
Gutter thickness and length dimensions
| Material | Common thicknesses | Source |
|---|---|---|
| Aluminum | 0.025 in low grade; 0.027 in typical for moderate climates; 0.032 to 0.040 in for ice-prone regions | HomeGuide aluminum guide |
| Aluminum (commercial) | 0.032, 0.040 and 0.050 in | DMI K-style product page |
| Galvalume and stainless steel | 22 and 24 gauge | DMI K-style product page |
| Painted steel box gutter | 24 gauge online, 26 gauge by quote | Sanders Metal |
| Copper | 16 oz (about 0.0216 in) and 20 oz (about 0.027 in) | DMI K-style product page |
- Aluminum: HomeGuide’s aluminum guide says contractors typically use 0.027 inch in moderate climates and 0.032 to 0.040 inch where ice is common, and calls 0.025 inch low quality. GutterAll sells its 5-inch K-style sections in 0.027 inch.
- Steel: DMI offers Galvalume and stainless K-style in 22 and 24 gauge; Englert’s 5-inch machine runs steel up to 24 gauge.
- Copper: measured by weight per square foot, with DMI offering 16 oz and 20 oz. Englert’s machine forms copper up to 20 oz, 3/4 hard.
- Vinyl: sold in sectional lengths, typically 10 ft, and not roll-formed on site.
Length works one of two ways. Seamless gutter is roll-formed from coil at the job site, and K&M Sheet Metal lists roll-formed 5 and 6 inch K-style in lengths up to 40 feet. Sectional gutter comes in stock lengths, such as GutterAll’s 10 ft and 20 ft sections, joined with slip connectors that add seams to seal. For how thickness and material trade off on price and life, compare gutter materials side by side.
Which gutter dimensions fit your roof
Pick gutter dimensions from roof area and rainfall, not habit. IPC Equation 11-1 converts rain to flow at 0.0104 gpm per square foot of roof per inch per hour, so a design storm of 4 inches per hour puts about 0.042 gpm on each square foot. Size the trough to the drainage area first, then match the downspout to the trough. Find your rainfall rate in NOAA’s Atlas 14 precipitation frequency server.
| If the roof area draining to one run is | Use at least | Basis at 4 in/hr |
|---|---|---|
| Up to about 1,780 sq ft | 5-inch gutter, 2 x 3 or 3 x 4 downspout | 5 in semicircle rated 74 gpm (IPC Table 1106.6) |
| About 1,780 to 2,640 sq ft | 6-inch gutter, 3 x 4 downspout | 6 in semicircle rated 110 gpm |
| About 2,640 to 5,940 sq ft | 8-inch gutter or split the run with more outlets | 8 in semicircle rated 247 gpm at 1/8 in per ft |
| Rainfall rate other than 4 in/hr | Multiply the areas by 4, then divide by your rate | IPC Equation 11-1 |
The IPC rates semicircular and rectangular shapes, not ogee K-style, and a K-style holds more than a half-round of the same width, so for K-style the table is a conservative guide. To run the numbers for your own house, use our method for choosing gutter sizes by roof area and capacity. If you already have gutters and just need to confirm what you own before buying guards or parts, start with how to measure gutter size.
Frequently asked questions
What are standard gutter dimensions?
Standard residential gutters are 5-inch or 6-inch measured across the top opening. In DMI’s table, a 5-inch K-style is 3-13/32 inches tall at the front, 3-13/16 inches at the back and 3-1/4 inches across the bottom, and a 6-inch K-style is 4-1/2, 5 and 3-7/8 inches. HomeGuide states that most homes use 5-inch K-style. Sizes of 7 and 8 inches are usually brake-formed for large or commercial roofs.
How wide is a 5 inch gutter really?
A 5-inch gutter measures 5 inches across the top opening, front to back. A 5-inch K-style also stands about 3-13/32 inches at the front and 3-13/16 inches at the back with a 3-1/4 inch bottom (DMI), and it is formed from 11-3/4 or 11-7/8 inches of flat coil (Lynch Aluminum). Its held cross-section is about 14 square inches, roughly 0.73 gallons per foot.
What is the most common gutter size?
The 5-inch K-style is the most common gutter size in the United States; HomeGuide’s October 2025 installation guide states that most residential homes use it. In regions with heavy rain, long roof planes or steep pitches, 6-inch K-style is the common upgrade, adding $1 to $2 per linear foot and holding about 58% more water per foot by a geometry estimate from DMI’s dimensions.
What size downspout goes with a 6 inch gutter?
A 6-inch K-style gutter should feed a 3 x 4 inch rectangular downspout, which has 12 square inches of opening, rather than the 6 square inch 2 x 3. In IPC Table 1106.3 the nearest listed leader, 3 x 4-1/4 inches, is rated 192 gpm. On large or commercial runs a 4 x 5 downspout (360 gpm) may be needed. A 6-inch half-round pairs with a 4-inch round downspout.
Are K-style and half-round gutters the same size?
No. A 5-inch K-style and a 5-inch half-round share the same nominal width but not the same capacity. The K-style holds about 14.1 square inches below its front lip against about 9.8 for a 5-inch semicircle, roughly 43% more. Half-round also hangs on brackets or straps and sits forward of the fascia, changing the mounting geometry.
What thickness should gutters be?
For aluminum, HomeGuide says 0.027 inch is typical in moderate climates and 0.032 to 0.040 inch suits ice-prone regions, while 0.025 inch is low quality. DMI offers Galvalume and stainless steel gutters in 22 and 24 gauge, and copper in 16 oz and 20 oz. Thicker stock costs more but resists denting and holds its shape under snow and ladder loads.