K-style gutters
By Gutter Report Editorial. Last reviewed August 2026. How we research this.
In brief
K-style is the gutter on most American houses. Amerimax defines it as a profile with an ogee curved front face, a boxed top bead and a stepped bottom, and ogee simply means a reverse curve. The back is flat, so it screws straight to the fascia with no brackets. A 5 inch K-style measures 5 inches across the top, 3 3/8 across the bottom and 3 5/8 deep, per the KM Sheet Metal submittal drawing. Sizes run 4 to 8 inches, and most houses use 5. It is the default because it is cheapest to hang, it looks like crown molding from the ground, and every seamless machine on every truck is set up to roll it. K-style is also the baseline in every price table on this site: half round costs $1 to $2 a foot more in the same metal.
1.0The actual dimensions
Most pages describe K-style and never measure it. These come from a manufacturer submittal drawing, KM Sheet Metal drawing D-001, K Style Ogee Gutter.
| Size | Top width | Bottom width | Back height | Front height |
|---|---|---|---|---|
| IN | IN | IN | IN | |
| 4K | 4 | 2 3/4 | 3 1/8 | 2 7/8 |
| 5K | 5 | 3 3/8 | 3 5/8 | 3 5/8 |
| 6K | 6 | 3 7/8 | 4 7/8 | 4 5/8 |
| 7K | 7 | 4 9/16 | 5 7/8 | 6 |
| 8K | 8 | 5 3/8 | 7 1/4 | 7 |
Notice the shape of the numbers. The bottom is always narrower than the top, because the ogee face steps in as it comes down. So a 5 inch gutter is 5 inches across the opening and about 3 3/8 across the floor, and that floor is what a downspout outlet has to fit inside.
One caution. Retailer listings give the depth of a 5 inch K-style as 3-3/4 inches in one place and 3.5 in another, and those are estimates from sellers rather than manufacturer figures. The table above is the manufacturer drawing, so use it.
The same drawing notes a real manufacturing split: 5 and 6 inch K-style are roll formed and available in lengths up to 40 feet, while 4, 7 and 8 inch are brake formed and top out at about 20 feet. That is why seamless in practice means 5 or 6 inch.
2.0What K-style stock costs
K-style is the volume profile, so it is the one that is genuinely cheap on a shelf. All read 2026-08-21.
| Item | Price | Per foot | Seller |
|---|---|---|---|
| USD | USD / FT | ||
| 5 in. vinyl, 10 ft | $9.98 | $1.00 | The Home Depot |
| 5 in. aluminum .0185, 10 ft | $12.98 to $17.98 | $1.30 to $1.80 | The Home Depot |
| 5 in. aluminum .0255, 10 ft | $19.99 | $2.00 | The Home Depot |
| 6 in. aluminum .0255, 10 ft | $27.98 | $2.80 | The Home Depot |
| 5 in. galvanized steel, 10 ft, mill finish | $10.79 | $1.08 | Hemlock Hardware |
| 5 in. aluminum coil stock, .032 | by the foot | $4.08 | Seamless Gutter Supply |
| 6 in. aluminum coil stock, .032 | by the foot | $5.27 | Seamless Gutter Supply |
| 5 in. copper, 16 oz | by the foot | $11.39 | Classic Gutter Systems |
| 6 in. copper, 20 oz | by the foot | $16.23 | Classic Gutter Systems |
Per foot figures on the section rows are our arithmetic. Compare the aluminum rows against the half round page, where the same 5 inch aluminum runs $3.58 at a supplier and $6.00 at a big box store. K-style is cheaper as stock, before any labor difference, because it is the profile everyone makes.
Installed, K-style is the baseline every publisher prices against. HomeGuide puts aluminum at $10 to $20 a foot installed, Fixr at $7 to $13, and Angi at $7 to $12. Half round adds $1 to $2. Run your own footage with the cost calculator or read the per foot breakdown.
3.0Back styles, and why they exist
The flat back of a K-style is not always flat in the same way. Berger lists four.
- Hemback. The top back edge is folded over on itself. The common residential back.
- Straight back. A plain unfolded back. What most big box sections are.
- Hi-back, 45 degree. The back extends up at an angle to tuck under the roof edge or a drip edge.
- Apron, 90 degree. The back extends up flat, which lets it run behind the shingle course.
Hi-back and apron exist for one job: keeping water that runs behind the drip edge from getting between the gutter and the fascia. If your fascia is rotting behind an otherwise working gutter, that is the problem those backs solve. See fascia repair cost.
Aluminum thickness varies by back style too. Amerimax lists straight back 5 inch at .0185, .0255 and .0305, and 6 inch at .0255. Its hem back comes 5 inch at .027 and .032, and 6 inch at .032, with a stated tolerance of plus or minus .002 inch. Berger runs galvanized K-style at 26 gauge in the common sizes.
4.0Capacity, and one number to stop repeating
Two capacity figures are quoted constantly for K-style. One is useful with a caveat. The other is impossible.
| Claim | Figure | Verdict |
|---|---|---|
| 5 in. K-style drainage area, Fine Homebuilding | 5,520 sq ft | Real, but only at 1 in. of rain per hour |
| 6 in. K-style drainage area, This Old House | 7,960 sq ft | Same basis by context, which the page does not state |
| 5 in. K-style water held, Modernize | 1.2 gal per ft | Not physically possible |
| 6 in. K-style water held, Modernize | 2 gal per ft | Same problem |
Take the impossible one first, because it is everywhere. Holding 1.2 gallons in a foot of gutter needs 23.1 square inches of cross section. A 5 inch K-style is 5 inches wide and 3 5/8 inches deep at most, so its entire bounding box is 18.1 square inches, and the real ogee section is well under that. The claim is off by roughly four to five times. That arithmetic is ours, run against the manufacturer dimensions in section 1.0.
Now the useful one. The 5,520 square foot figure comes from Fine Homebuilding, issue 125, and it is stated there at 1 inch of rain per hour. This Old House reprints the same number without the basis. The original article then does the step everyone drops: it divides 5,520 by Washington DC's five minute rainfall intensity of 6.6 inches per hour and gets 836 square feet of actual maximum roof area for one 5 inch gutter. That is the number a builder uses.
So a 5 inch K-style does not drain 5,520 square feet of roof anywhere in America. Divide by your own local intensity first. NOAA publishes it: the ten year, five minute intensity is 3.64 inches per hour in Los Angeles, 7.43 in Chicago and 10.8 in Miami, so the same gutter covers roughly three times more roof in Los Angeles than in Miami.
Two more things that change what one gutter can drain
The gutter size is one of four inputs, and the other three are easier to change.
- Slope. Fine Homebuilding states that pitching a gutter 1/8 inch per foot multiplies the drainable roof area by 1.4. Berger adds the limit: 1/16 inch per foot or less earns no credit at all and is treated as a level gutter.
- A second downspout. Going from one outlet to two doubles the roof area a section of gutter can drain, per the same Fine Homebuilding article. That is the cheapest capacity you can buy.
- Roof pitch. A steeper roof throws more water at the same plan area. The Copper Development Association publishes the factors, and This Old House publishes them identically: 1.00 for flat to 3 in 12, 1.05 for 4 to 5, 1.10 for 6 to 8, 1.20 for 9 to 11, 1.30 for 12 in 12 and steeper. Multiply your plan area, not the sloped area, by the factor.
Publishers disagree on how far one downspout can carry. Amerimax says one downspout every 20 feet of gutter. The Copper Development Association caps one at 50 feet. This Old House says runs of 60 feet or longer need at least two outlets. Three numbers for three different reasons, and the conservative one is Amerimax's.
5.0You may not need to change profile
K-style is already on your house, and switching profiles is one of the more expensive things you can do for the least performance change. New brackets, new outlets and new hangers along the entire run, to get a gutter that drains no better.
If the complaint is overflow, the fix is in section 4.0 and none of it is a profile: add a downspout, correct the slope, clear the run, or move up to 6 inch. If the complaint is a drip, it is a seam or a hanger, and a repair at a national average of $275 covers it. We can say that plainly because we do not sell gutters and we do not install them.
The honest reason to change to half round is that the house is a period style and the ogee face looks wrong on it. That is a real reason. It is just not a drainage reason.
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Common questions
What is a K-style gutter?
A gutter with an ogee curved front face, a boxed top bead and a stepped bottom, per the Amerimax glossary. Ogee just means a reverse curve, and it is another name for the same profile. The back is flat, which is what lets it screw straight to the fascia board. The K is not a shape description; it is a style designation the trade kept.
What are the dimensions of a 5 inch K-style gutter?
From the KM Sheet Metal submittal drawing for K-style ogee gutter, a 5K measures 5 inches across the top, 3 3/8 inches across the bottom, and 3 5/8 inches at the back and at the overall front height. A 6K measures 6 inches across the top, 3 7/8 at the bottom, 4 7/8 at the back and 4 5/8 at the front. Those are manufacturer figures, not estimates.
What sizes do K-style gutters come in?
Widths of 4 to 8 inches, with most homes on 5 inch, per Modernize. Berger Building Products stocks 5, 6, 7 and 8 inch. Englert lists 3 through 8. One practical split: 5 and 6 inch are roll formed and available up to 40 feet, while 4, 7 and 8 inch are brake formed and top out around 20 feet.
How much roof can a 5 inch K-style gutter drain?
Fine Homebuilding gives 5,520 square feet at 1 inch of rain per hour, and 7,960 for a 6 inch. That basis matters and most reprints drop it. The same article divides 5,520 by Washington DC rainfall intensity of 6.6 inches per hour and gets 836 square feet of real maximum roof area. A page quoting 5,520 as a usable roof area is off by roughly seven times.
How much water does a 5 inch K-style gutter hold per foot?
Less than the number you have probably read. The figure of 1.2 gallons per linear foot circulates widely, and it is not physically possible: 1.2 gallons per foot needs 23.1 square inches of cross section, and a 5 inch K-style whose entire bounding box is 5 by 3 5/8 inches cannot exceed 18.1 square inches. The matching claim of 2 gallons for a 6 inch has the same problem. That arithmetic is ours.
Why is K-style the default?
Three practical reasons. The flat back screws directly to fascia, with no brackets to buy or space. The decorative front face resembles crown molding, which suits most postwar houses. And it is what every seamless machine on every truck is set up to roll, so it is the cheapest profile to get formed on site.
- Rev
- RevAugust 2026
- Source
- SourceKM Sheet Metal, Amerimax, Berger, Fine Homebuilding, This Old House, CDA, NOAA (read 2026-08-21)