How to Choose the Right Gutter Size

Gutter Sizing Guide

Gutters come in various sizes, each with a different capacity. Sometimes it can be tricky. A 5″ OGEE or Straight-Face gutter carries the same capacity as a 6″ half-round. 6″ OGEE and straight-face have a 40% larger capacity than 5″ gutters. A 7″ gutter will have an even larger capacity, but that’s not always the reason to go to 7″.

What factors should I consider when choosing a size?

The factors we consider when choosing a size go in this order:

1) Roof Type

This part is pretty simple. 5″ gutters can only possibly work on a composite shingle roof, assuming there are adequate downspouts and not a massive volume of water. Metal and clay tile roofs shed water too quickly. The gutter is often much lower than the top of the roofline, so the water “shoots” over the gutter and misses it entirely. The measurement we are referencing (5″, 6″, and 7″) is the measurement of the mouth of the gutter, or from the back to the widest part of the front. At Gutter King, metal roofs and slate tile roofs automatically get upgraded to 6″ gutter so we can ensure the water doesn’t miss the gutter. Because of the channels formed in the tile, barrel tile roofs need an even larger opening of 7″, so we always recommend 7″ gutters on barrel tile roofs. In most cases, barrel tile roofs shed a lot of water. 

  • Composite shingle roofs – 5″ gutter is usually acceptable
  • Metal Roofs (standing seam and screw-down) and slate tile: 6″ is necessary
  • Barrel Tile Roofs – 7″ gutter is best

2) Downspout locations and length of run

The “Bottleneck” in your gutter system will always be your downspouts. There are a couple of rules that we try to follow whenever we can. First, we never want to go more than 35′ of roofline before we get to a downspout. Second, we need to ensure the spouts have the proper capacity ratings. It’s also imperative that the hole in the gutter going into the downspout isn’t smaller than the downspout; otherwise, you’re limited to the hole’s capacity. Each 3″x4″ downspout handles about 1200 s/f of roof plan from a bird’s eye view. If we need to exceed the 35′ or we don’t have enough capacity with the downspout, upgrading your gutter size is a good idea to allow time for the gutter to drain before it overflows.

3) Water capacity

It may come as a surprise that water capacity makes the third consideration. As we mentioned in the earlier two points, if the water can’t overshoot the gutter, and there are plenty of drainage points, then capacity isn’t a concern. Gutters are designed to move water, not hold water. However, water capacity is often considered when we see a very large roofline with heavy-flow points and valleys. These are often addressed with valley shields, but sometimes it’s better safe than sorry.

4) Region

Really? Absolutely! If you’ve ever spent time in places like California, you’ll notice that most of the rain they get comes in reasonably gently. Showers aren’t necessarily gully-washers, and most of the time, the water from a roof will flow gently into a small gutter and not overshoot it. If you’ve been in Texas any time, you’ve probably noticed that it pours when it rains. Our large storm systems will often drop several inches of rain in a brief period, and you want to be prepared for the heaviest rains, not the lightest ones. At a minimum, Gutter King recommends 6″ gutters on EVERY house in Texas.

5) Style

Gutter King is all about the look and functionality of your system. Many customers prefer the look of a 6″ gutter over a 5″ gutter simply because they look nicer. A 5″ gutter often looks like something is hanging on a fascia. The height of the gutter is smaller than the height of the fascia. With a 6″ fascia, the gutter often completely fills the fascia, and it blends in nicely. Our 6″ straight-face gutter even mimics the look of a traditional trim board.


Homeowners will likely be given a wide variety of options for their home, including multiple sizes, materials, styles, guards, etc., for their gutter system. A professional must help you determine the correct size for your home to ensure your system is functional under every condition. Gutter King will always recommend you consider a 6″ Gutter over a 5″ because of the large storms and heavy downpours. Should you find yourself on the fence of one size, you’ll never regret going up a size, but you might regret going down.

Choose the Gutter Company Austin, Texas Homeowners Can Trust

At Austin Gutter King, we have over twenty years of expertise in helping our clients find the gutters they need. Regarding gutter installation, Austin, Texas, residents know they can rely on Austin Gutter King. Contact us for a free consultation to help you choose the right gutter size!

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