6 inch gutters
By Gutter Report Editorial. Last reviewed August 2026. How we research this.
In brief
A 6 inch gutter carries about 40 percent more water than a 5 inch and costs about 30 to 40 percent more in metal. Englert publishes the 40 percent figure, and This Old House roof area numbers, 5,520 square feet for 5 inch K-style against 7,960 for 6 inch, imply 44 percent. On price, a 10 foot aluminum section runs $19.99 in 5 inch and $27.98 in 6 at The Home Depot, and trade .032 coil runs $4.08 a foot against $5.27. Labor hardly changes, so the whole job delta is smaller than that. Upsize when the roof area is large, the pitch is steep, local rainfall is intense, or the run is long with few outlets. One rule comes with it: Amerimax says 6 inch systems take 3 by 4 inch downspouts only, not 2 by 3.
1.0What the size step costs
| Item | 5 inch | 6 inch | Step up |
|---|---|---|---|
| USD | USD | PERCENT | |
| Aluminum K-style .0255, 10 ft section | $19.99 | $27.98 | 40 |
| Aluminum K-style .0255, 16 ft section | $32.98 | $44.98 | 36 |
| Aluminum coil stock .032, per foot | $4.08 | $5.27 | 29 |
| Half round aluminum, per foot | $3.58 | $4.73 | 32 |
| Half round Galvalume 26 ga., per foot | $3.58 | $4.73 | 32 |
| Half round copper 16 oz, per foot | $10.94 | $13.03 | 19 |
| Aluminum material, HomeGuide, per foot | $1 to $4 | $2 to $5 | n/a |
The percentages are our arithmetic on the listed prices. The 5 inch aluminum rows come from The Home Depot and the coil and half round rows from Seamless Gutter Supply and Classic Gutter Systems, all read 2026-08-21.
There is a physical reason the step is about a third. A 5 inch K-style is formed from coil 11-3/4 or 11-7/8 inches wide, and a 6 inch from coil 15 inches wide. That is 28 percent more metal, and Englert's own yield table agrees: at .032 thickness, 11-3/4 inch coil gives 2.238 feet of gutter per pound and 15 inch coil gives 1.754, which is 28 percent heavier per foot. So you pay roughly 28 percent more metal for roughly 40 percent more capacity, which is the whole case for 6 inch.
Labor is the part that does not scale. Hanging a 6 inch run takes the same hangers at the same spacing on the same fascia. That is why the installed price gap between the sizes is smaller than the material gap. Run your own numbers with the cost calculator.
2.0How much more water, honestly
| Source | Claim | Implied increase |
|---|---|---|
| PERCENT | ||
| Englert | 6 inch handles about 40 percent more water | 40 |
| This Old House | 5,520 sq ft at 5 inch, 7,960 at 6 inch | 44 |
| Modernize | 1.2 gal per foot at 5 inch, 2 gal at 6 inch | 67 |
Two of the three agree and the third does not, so it is worth saying why we drop it. The Modernize figures fail arithmetic. Holding 1.2 gallons in one 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 its largest, per the KM Sheet Metal submittal drawing, so its whole bounding box is 18.1 square inches and the real ogee section is smaller still. The claim is off by roughly four to five times, and the 2 gallon figure for 6 inch shares the error. That check is ours.
Use 40 percent. It is the figure a manufacturer publishes and the figure the independent roof area numbers support.
Note also that the This Old House roof area figures carry a hidden basis. Their source, Fine Homebuilding issue 125, states 5,520 square feet at 1 inch of rain per hour, then divides by the local five minute rainfall intensity to get a usable number. In Washington DC, at 6.6 inches per hour, that is 836 square feet, not 5,520. Use the ratio between the sizes, not the raw figures.
3.0When to go to 6 inch
Four conditions push a house past 5 inch. Any one of them can be enough, and they stack.
- Large roof area on one run. A long unbroken elevation, or a big roof plane draining to a single gutter.
- Steep pitch. A steeper roof throws more water at the same footprint. The Copper Development Association and This Old House publish identical factors: 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 the plan area, not the sloped area.
- Intense local rain. This is the input people skip and it swings the most. NOAA's ten year, five minute intensity is 3.64 inches an hour in Los Angeles, 7.43 in Chicago and 10.8 in Miami. The same gutter covers roughly three times more roof in Los Angeles than in Miami.
- Long runs with few outlets. Amerimax recommends a downspout every 20 feet, the Copper Development Association caps one at 50 feet of gutter, and This Old House says runs of 60 feet or longer need at least two outlets. If your run breaks all three rules, the gutter is not the only problem.
Valleys are the case nobody warns about. Where two roof planes meet, the valley dumps a concentrated stream into one short stretch of gutter, and that stretch overflows while the rest of the house is fine. Upsizing the whole house for one valley is the expensive answer; an outlet near the valley is the cheap one.
4.0The downspout rule that comes with it
A bigger gutter feeding the same downspout just moves the bottleneck. Amerimax states the pairing plainly: 5 inch systems can use 2 by 3 or 3 by 4 inch downspouts, and 6 inch systems use 3 by 4 only.
| Downspout | Roof area served |
|---|---|
| SQ FT | |
| 2 x 3 in. rectangular | about 600 |
| 3 x 4 in. rectangular | up to 1,200 |
| 3 in. round | about 706 |
| 4 in. round | up to 1,255 |
This Old House and Modernize publish these four figures identically. The underlying rule of thumb is one square inch of downspout for every 100 square feet of roof, which Texas A&M AgriLife Extension, This Old House and Fine Homebuilding all give.
One caution on those numbers. They use the geometric area of the downspout, and a SMACNA method calculator uses smaller effective areas: 4.8 square inches for a 2 by 3 against 6.0 geometric, and 10.31 for a 3 by 4 against 12.0. Sizing off geometric area overstates what a downspout can carry by roughly 14 to 20 percent. Costs for the vertical work are on the downspout installation page.
Cheaper capacity than a bigger gutter
Before you price re-hanging the house in 6 inch, there are two changes that buy more capacity for less money.
- Add a downspout. Fine Homebuilding states that going from one outlet to two doubles the roof area a section of gutter can drain. That is 100 percent against the roughly 40 percent that upsizing buys, for the price of an outlet, a run of downspout and a few brackets.
- Pitch the gutter. The same article gives a 1.4 times multiplier for pitching at 1/8 inch per foot. Berger adds the catch: 1/16 inch per foot or less earns no credit and is treated as a level gutter, so a token slope buys nothing.
Slope is also where the trade disagrees with itself, so ask what your contractor uses. This Old House and Modernize call 1/4 inch per 10 feet standard. Engineering LibreTexts says 1/2 inch per 10 feet. Texas A&M and Fine Homebuilding call for 1/16 inch per foot, which is 5/8 inch per 10 feet, two and a half times steeper than the This Old House figure. The plumbing code tabulates gutter capacity at 1/16, 1/8, 1/4 and 1/2 inch per foot but does not mandate a minimum.
Doing both, two outlets and a real pitch, gets a 5 inch gutter past what a 6 inch gutter does on its own.
5.0You may not need 6 inch
Most people asking about 6 inch gutters are not sizing a new house. They have 5 inch gutters that overflow in a hard rain, and someone told them to go bigger.
Overflow has four common causes and only one of them is gutter size. A clogged run backs up at any size. A run pitched wrong, or with a low spot, holds water and spills at the low point. Too few downspouts is the most common of all, and it is the cheapest to fix. Water shooting over the front edge off a steep roof can be a drip edge problem, where the water never lands in the gutter at all.
Work through those first. If they are all correct and it still overflows in ordinary rain, then the gutter is undersized and 6 inch is the right answer. A repair at a national average of $275, or one added downspout, answers this complaint more often than a whole house resize does. We can say that plainly because we do not sell gutters and we do not install them.
If you are replacing everything anyway, the calculus changes. The metal costs about a third more, the labor is the same, and you never have to think about it again. See replacement cost, and pick the profile on the K-style and half round pages.
Get a gutter sizing quote from a licensed contractor
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Common questions
How much more do 6 inch gutters cost than 5 inch?
About 30 to 40 percent more for the metal, and less than that as a share of the whole job. At The Home Depot a 10 foot aluminum K-style section is $19.99 in 5 inch and $27.98 in 6 inch, 40 percent more. Trade .032 coil runs $4.08 a foot in 5 inch and $5.27 in 6, 29 percent more. HomeGuide puts 5 inch aluminum material at $1 to $4 a foot and 6 inch at $2 to $5. Labor barely changes, so the delta on a whole house is smaller than the metal delta suggests.
How much more water does a 6 inch gutter carry?
About 40 percent more. Englert states that outright, and This Old House roof area figures of 5,520 square feet for 5 inch K-style and 7,960 for 6 inch imply 44 percent, which agrees. Modernize implies 67 percent by way of a per foot volume claim that fails arithmetic, so we do not use it. Plan on 40 percent.
Do I need 6 inch gutters?
Four things push you there: a large roof area feeding one run, a steep pitch that throws more water at the same footprint, high local rainfall intensity, and a long run with few downspouts. Any one can be enough. If none of those describes your house, 5 inch is the size the trade defaults to for a reason.
Do 6 inch gutters need bigger downspouts?
Yes, and this is the part that gets skipped. Amerimax states that 5 inch systems can use 2 by 3 or 3 by 4 inch downspouts, while 6 inch systems use 3 by 4 only. A 2 by 3 downspout serves about 600 square feet of roof and a 3 by 4 serves up to 1,200, per This Old House. Fitting 6 inch gutter to 2 by 3 downspouts moves the bottleneck rather than removing it.
Is 6 inch gutter worth it if I add a downspout instead?
Often the downspout wins. Fine Homebuilding states that going from one downspout to two doubles the roof area a section of gutter can drain, which beats the roughly 40 percent that upsizing buys, and costs far less. Pitching the gutter 1/8 inch per foot multiplies capacity by 1.4 on its own. Try those before you re-hang the house.
What sizes are there besides 5 and 6 inch?
K-style is made from 4 to 8 inches and half round from 4 to 8 as well. Berger stocks 5, 6, 7 and 8 inch K-style. One practical limit: 5 and 6 inch are roll formed and come in lengths up to 40 feet, while 4, 7 and 8 inch are brake formed and top out near 20 feet, so seamless in practice means 5 or 6 inch.
- Rev
- RevAugust 2026
- Source
- SourceEnglert, Amerimax, KM Sheet Metal, Fine Homebuilding, This Old House, CDA, NOAA (read 2026-08-21)