It’s a classic St. Louis spring storm. Rain is coming down sideways, and you glance out the window to see a sheet of water pouring straight over the front edge of your gutters like a little waterfall. The gutters are there. They’re just not keeping up. Nine times out of ten, homeowners assume it’s a clog. Just as often, the real culprit is size.
Gutter size is one of those things nobody thinks about until water is going somewhere it shouldn’t. Get it right and your gutters quietly do their job for years. Get it wrong and you’re looking at overflow, soggy landscaping, and water pooling against your foundation, which is a much bigger headache than the gutters ever cost. So let’s walk through the three sizes you’ll actually be choosing from, what sets them apart, and how to land on the right one for your home.
The Three Sizes at a Glance
Residential gutters basically come in three sizes. Here’s the quick version before we get into the weeds.
| Size | Water capacity | Best for | Rough installed cost (per foot) |
|---|---|---|---|
| 5-inch | Baseline | Smaller roofs, average rainfall, a lot of older homes | $5 to $9 |
| 6-inch | About 40% more than 5-inch | Larger or steeper roofs, heavy rain, most new builds | $7 to $13 |
| Oversized (7-inch) | A big jump over 6-inch | Huge roofs, commercial buildings, extreme runoff | $12 and up |
Prices swing with material, how high your gutters sit off the ground, and local labor, so treat these as ballpark numbers, not a quote.
5-Inch vs 6-Inch: The Choice Most Homeowners Are Actually Making
This is the one you’ll probably be deciding, and it really comes down to a single question: how much water can the gutter move when the sky opens up?
A 5-inch K-style gutter has been the go-to for decades, and for an average roof in an average rain, it does the job just fine. A 6-inch K-style gutter, though, carries roughly 40% more water. That difference has nothing to do with what you notice from the ground. It’s about what happens during a hard, fast downpour, which, if you’ve lived through a St. Louis August, you know is exactly when a too-small gutter gives up. If you want to geek out on the numbers, we broke down how much water a 6-inch gutter can actually handle in a separate post.
Here’s the part people skip: the downspout matters just as much as the gutter. Five-inch gutters usually run 2×3 inch downspouts, while 6-inch gutters use bigger 3×4 inch downspouts that drain more than twice the water. A wider gutter feeding a bigger downspout is what keeps the whole system from backing up when it counts. Size up the gutter but leave the downspout alone, and all you’ve done is move the traffic jam.
One quick note on shape: most homes use K-style gutters, but if you’re weighing looks against capacity, our take on K-style vs half-round is worth a read.
Oversized Gutters: When Bigger Is Genuinely Better
“Oversized” usually means a 7-inch gutter, and it exists to solve one specific problem: too much water showing up in one spot, too fast.
You do not need oversized gutters on a typical house, and any contractor pushing them on a standard roof is selling, not advising. Where they earn their keep is on homes and buildings where the roof simply overwhelms a normal gutter. A few situations point that direction:
A big roof, where one gutter run has to catch water off a wide stretch of shingles. A steep pitch, which fires water into the gutter faster and harder than a gentle slope. Roof valleys that dump two planes of runoff into a single section, creating a concentrated gush every time it storms. And heavy, intense rainfall, because your gutters have to survive the worst downpour, not the average Tuesday drizzle.
If a couple of those describe your place, oversized gutters stop being an upgrade and start being the right tool. This is especially common on commercial and industrial buildings, which is a whole conversation of its own. We cover it in our guide to commercial gutter sizes. For most standard rooflines, a well-installed 6-inch system handles everything you throw at it without the extra cost.
What’s the Real Cost Difference?
Bigger gutters cost more, and it’s worth knowing why so the price actually makes sense.
Going from 5-inch to 6-inch usually adds a few dollars per linear foot. The gutter uses more material, the larger downspouts cost more, and the heavier runs take a bit more labor to hang right. Across a whole house that adds up, but it’s rarely the number that should decide it. Compare it against the cost of fixing overflow damage to your fascia, siding, or foundation, and the upgrade tends to look pretty cheap. Material plays a role too, so it’s worth glancing at the pros and cons of different gutter materials before you settle on a number.
Oversized 7-inch gutters sit at the top of the range. They eat up more material, often need custom fabrication, and are heavier to install, so both the product and the labor climb.
The honest way to think about it: the cheapest gutter isn’t the one with the lowest price per foot. It’s the one that’s actually sized to handle your roof, because a system that overflows is the expensive option no matter what you paid for it.
Size and Downspouts Go Together
We touched on this above, but it’s worth its own line. The right gutter size feeding too few or too small downspouts will still overflow, because the water has nowhere to go fast enough. Rule of thumb: the bigger the gutter, the bigger and more frequent your downspouts should be. Before you lock in a size, take five minutes with our breakdown of how many downspouts your home needs so you’re planning the whole system, not just half of it.
So, Which Size Do You Actually Need?
You can narrow it down with four quick questions:
How big is your roof? More square footage means more water in every run, which leans you toward 6-inch or bigger. How steep is it? A steep pitch moves water faster and favors more capacity. How much rain do you get, and how hard? Plan around the gully-washers, not the sprinkles. And how many trees hang over the house? Heavy leaf load makes a bigger gutter more forgiving and easier to keep flowing.
If your answers are “small roof, gentle slope, average rain, not many trees,” 5-inch will likely treat you well. The more your answers tip the other way, the stronger the case for 6-inch, and in the extreme cases, oversized.
Not Sure Which Size Fits Your Home? Let’s Figure It Out.
The best gutter size is the one matched to your specific roof, not whatever a crew reaches for out of habit. If you’re in the St. Louis metro and you’d rather get a straight answer than a guess, we’ve got the tools and the experience to help. GutterPros will look at your roof, your runoff, and your drainage, then recommend the right size with zero pressure to oversize just for the sake of it.
Contact us for a free gutter sizing assessment and get it done once, done right.