What Size Gutter Do I Need for My Home?

Wondering what size gutter you need for your home? This guide will help you choose the right size gutters for your home and ensure proper drainage.

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Gutters and Downspouts

Gutters are important for any home as they help to direct water away from your foundation and prevent pooling around your home. But what size gutter do you need for your home? There are a few factors to consider when choosing the right size gutter for your home.

Gutter Sizes

The size of the gutters you need depends on the size and slope of your roof. The tables below show the recommended gutter size for different roof sizes and slopes.

Roof Size Slope Gutter Size
≤1,200 sq. ft. ≥4″ per 10′ 5″
1,200-2,000 sq. ft. 3″-4″ per 10′ 6″
2,000-3,000 sq. ft. 2″-3″ per 10′ 7″
>3,000 sq. ft. <2" per 10' 8" Gutter sizes are measured in inches, and the most common sizes are 5", 6", and 7". Larger gutters (8" and up) are typically used on commercial buildings or homes with very large roofs.

Downspout Sizes

Downspouts, also known as leader pipes or drainspouts, are the vertical pipes that carry rainwater from your gutters down to the ground. They come in a variety of sizes and materials to suit different homes and needs.

The size of your downspouts should be based on the size of your gutters. Most experts recommend that you have at least two downspouts for each gutter, and that each downspout be at least half the size of the gutter it is attached to. For example, if you have a 5-inch gutter, each downspout should be at least 2.5 inches wide.

The most common sizes for residential gutters are 5 inches and 6 inches. The most common sizes for residential downspouts are 2 inches, 3 inches, and 4 inches.

If you live in an area with heavy rains, or if your home has a lot of trees nearby, you may need larger gutters and downspouts to handle the increased volume of water.

How to Measure for Gutters

Before you can order or install gutters, you need to take some measurements. You’ll need to know the length of the gutter run, which is the distance from the edge of the roof to the ground. You’ll also need to know the slope, or pitch, of the roof so that you can calculate how much rainfall the gutters will need to handle.

Measuring the Length

To start, you need to know the length of the gutter you need. To do that, follow these steps:

1. Measure the length of your home’s gable end in feet. This is the wall that has the triangular shape at the top.
2. Multiply that number by two, which will give you the total length of all four sides of your home.
3. Add ten feet to that number to account for the downspouts (two downspouts per 20 feet of gutter).
4. Divide the total number of feet by 3, which is the average length of a standard 10-foot section of gutter. This will give you the total number of 10-foot sections you need to purchase.

Measuring the Pitch

There are a few ways you can measure the pitch of your roof. If you have easy access to your roof, the most accurate way to measure is by using a level. Place the level on your roof so that one end is at the edge of your roof and the other is hanging over the edge. Have someone hold the level while you measure the distance from the bottom edge of the level to the gutter below. This will give you the rise. To get the run, measure the length of the level. Divide the rise by the run to get your pitch (example: 3 in 12 would be 3 ÷ 12 = .25 or ¼ pitch).

Another way to measure pitch is to take a long board and place it on your roof so it hangs over the edge. Again, have someone hold it while you measure from the end of the board that’s resting on your roof to the gutter below. This will give you your rise. To get your run, measure from one end of the board to the other. Divide rise by run (example: if your board is 10 feet long and it’s 3 inches from roof to gutter, then 10 feet ÷ 3 inches = 3.33 or 3 1/3).

Measuring the Size of the Downspouts

It’s important to factor in the size of your downspouts when measuring for gutters. To do this, you’ll need to know the square footage of your roof. Once you have that number, divide it by two to get the linear footage of your roofline. For example, if your roof is 1,600 square feet, that would be 800 linear feet.

Now that you know the linear footage of your roofline, you can determine the size of your downspouts. The rule of thumb is that you should have one square inch of downspout for every 600 square feet of roofline. So, using the 1,600 square foot roof from our earlier example, you would need two 2-inch diameter downspouts (800 square feet / 600 = 1.33).

How to Choose the Right Gutter Size

Your home’s gutter size is an important factor in keeping your home protected from water damage. If your gutters are too small, they can become overwhelmed during a heavy rainstorm and may overflow, spilling water onto your home’s exterior and foundation. If your gutters are too large, they may be too heavy for your home’s fascia and may cause your gutters to sag or even break off of your home. So, how do you know what size gutters you need for your home?

Square Footage of the Roof

The size of your roof is the primary factor that determines the size of the gutters you need. To calculate the square footage of your roof, simply measure the length and width of each section and multiply to get the square footage of that section. Then, add up all of the squares together to get the total square footage for your roof.

For instance, if your home has two stories and you have a section of roof that is 10 feet wide by 20 feet long on the first story and a second section that is 30 feet wide by 40 feet long on the second story, your calculation would look like this:

First Story: 10 x 20 = 200 sq. ft.

Second Story: 30 x 40 = 1,200 sq. ft.

Total Roof Square Footage: 200 + 1,200 = 1,400 sq. ft.

Number of Stories

The number of stories your home has will play a large role in determining the size of the gutters you need. A single-story home will require smaller gutters than a two- or three-story home. This is because the amount of water that needs to be drained from the roof increases with the number of stories.


When choosing the right gutter size for your home, one of the most important factors to consider is climate. The amount of rainfall your area receives on an annual basis will impact the size of gutters you need to properly protect your home from water damage.

For example, if you live in an area that experiences a large amount of rainfall, you’ll need gutters that can handle that volume of water. On the other hand, if you live in a drier climate, you may be able to get away with smaller gutters.

Other factors to consider when choosing the right gutter size include the type of roof you have and the slope of your roof. If you have a large roof or a roof with a steep slope, you’ll need larger gutters to prevent water from overflowing.

To sum it up, climate, roof size and slope, and home style are all important factors to consider when choosing the right gutter size for your home.

Roof Type

The first factor you need to consider in choosing the right size gutter is the type of roof. A standard asphalt shingle roof will generate about 28 to 38 gallons (106 to 144 liters) of water for each 100 square feet (9.3 square meters) of roof during a one-inch (2.54 centimeters) rainstorm. A metal roof will generate half as much runoff, while a thatched roof will generate about double the runoff of an asphalt shingle roof.