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What Size Gutters Should I Get? 12 Factors To Consider With Instructions & Calculations Included

Posted on July 27, 2023

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What Size Gutters Should I Get? 12 Factors To Consider With Instructions & Calculations Included

Imagine this: heavy rain pouring down on your property, but instead of water flowing smoothly through your gutters, you find yourself facing overflow, water spilling over the edges, and potentially damaging your home’s foundation. If you want to avoid this nightmare, it’s crucial to get the right gutter size for your house. This comprehensive guide will explore the essential factors to consider when determining the perfect gutter size that suits your specific needs.

Why Gutter Size Matters

Let’s begin with the basics. Gutters play a pivotal role in safeguarding your home against water damage. They collect rainwater from the roof and direct it away from the foundation. However, the size of your gutters significantly impacts their functionality. If your gutters are too small, water overflows, causing erosion, structural problems, and even basement flooding.

On the contrary, oversized gutters might not efficiently direct water away from your home, allowing debris to settle and clog the system. Finding the right balance between gutter size, rainwater volume, and downspout capacity is key. 

Factors to Consider When Choosing Gutter Sizes

1. Roof Area and Rainfall Intensity

The size of your roof and the intensity of rainfall in your area significantly impact the amount of water that gutters must handle. A larger roof with heavy rainfall necessitates gutters with a higher capacity to prevent overflow and water damage.

2. Type of Gutter Material

Gutters come in various materials like aluminum, vinyl, steel, and copper. Each material has different properties and levels of durability, which may influence the appropriate gutter size for your specific needs.

3. Gutter Style and Shape

Gutters are available in different styles, such as K-style and half-round, and various shapes that affect their capacity to handle water flow. Consider both aesthetics and functionality when choosing the right style and shape.

4. Number of Downspouts

Downspouts are essential for directing water away from your home’s foundation. The more downspouts you have, the better water flow and drainage you can achieve.

5. Gutter Capacity

Gutter capacity refers to the volume of water a gutter can handle. Larger gutters offer a higher capacity and are suitable for areas prone to heavy rainfall.

6. Installation Slope

Proper installation with the correct slope ensures efficient water flow toward the downspouts. This slope can influence the size of the gutters needed.

gutter materials
Gutter materials

7. Budget and Cost Considerations

Your budget is a crucial factor in the decision-making process. Balancing cost with functionality is vital when selecting the right gutter size.

8. Climate and Weather Conditions

Consider the climate in your region, including snowfall or extreme weather patterns, as it may impact your gutter’s performance and durability.

9. Maintenance and Cleaning

If you prefer low-maintenance gutters, one option is to install a gutter guard. A gutter guard is a physical barrier that prevents debris from entering the gutters. This can help to reduce the amount of time you spend cleaning your gutters.

10. Aesthetics and Curb Appeal

Gutters contribute to your home’s overall aesthetics. Choose a size and style that complements the architectural design and enhances your curb appeal.

11. Local Building Codes and Regulations

Some areas have specific building codes or regulations related to gutter size and installation. Check the codes in your area to ensure compliance with local guidelines.

12. Professional Advice and Recommendations

When in doubt, consult a professional gutter installer. They can assess your specific requirements and provide expert recommendations for the ideal gutter size.

Instructions for Measuring Gutter Size

Now that you’re aware of the factors affecting gutter size, it’s time to take matters into your own hands and measure the perfect fit for your home. Follow these simple steps:

Step 1: Gather the Necessary Tools

Before you begin, gather the tools you’ll need: a measuring tape, ladder, pencil, paper, and a calculator.

Step 2: Measure the Roof Perimeter

Climb the ladder and carefully measure the perimeter of your roof using the measuring tape. Make a note of each section’s length.

Step 3: Calculate the Area of the Roof

With the lengths of all sections on hand, calculate the roof area by multiplying the length of each section by its corresponding width. Add the areas of all sections to get the total roof area.

Step 4: Determine the Gutter Slope

The recommended slope for gutters is ¼ inch per 10 feet of gutter. Adjust this slope according to your roof length and shape.

Step 5: Consider Downspout Placement

Plan the placement of downspouts based on your roof layout to ensure efficient water drainage.

Calculating the Appropriate Gutter Size

Now that you have the roof area and slope information, let’s calculate the appropriate gutter size using a standard formula:

Gutter Size (in inches) = (Roof Area in square feet) / (Gutter Slope x 12 inches)

  • Example Calculation for a Residential Property:

Assume your roof area is 2,000 square feet, and the recommended slope is ¼ inch per 10 feet.

Gutter Size = (2,000 sq. ft.) / (0.25 x 12) = 6.67 inches

Based on this calculation, you would need 6.67-inch gutters for your residential property.

  • To find the right gutter size, you’ll also need to calculate the drainage area:

1. For a simple gable roof, make two separate calculations for each slope.

2. If your roof has multiple facets, calculate the drainage area for each surface to determine the total square footage.

  • Utilize the roof-pitch factor to finalize the gutter size:

1. The roof-pitch factor indicates the steepness of your roof and can be determined using a two-foot level and a tape measure.

2. Place one end of the level against the roof, then measure the distance between the middle of the level and the roof beneath it. This measurement is the 12-inch run.

3. Refer to the table below to find your roof-pitch factor based on your measurement:

                   Roof Pitch                Roof Pitch Factor
12/12 or higher                         1.3
9/12 to 11/12                         1.2
6/12 to 8/12                         1.1
4/12 to 5/12                        1.05
0/12 to 3/12                         1.0

After taking the necessary measurements, you’re ready to determine the right gutter size for your home. Multiply the roof’s drainage area by the roof-pitch factor and maximum rainfall intensity to get the adjusted square footage.

  • For k-style or half-round gutters, use the following guidelines based on the adjusted square footage:
  1. K-Style Gutters:
  • Five-inch gutters for areas under 5,520 square feet
  • Six-inch gutters for areas between 5,530 and 7,960 square feet
K-Style Gutter
  1. Half-Round Gutters:
  • Five-inch gutters for areas under 2,500 square feet
  • Six-inch gutters for areas between 2,500 and 3,840 square feet
half round gutter

Always opt for the largest gutter size if your roof has different drainage areas. For example, if a house in Los Angeles has a drainage area of 1,000 square feet with a pitch factor of 1.05 for 5/12, the adjusted square footage is 2,835 square feet, ideal for a five-inch half-round gutter.

Don’t forget the importance of downspouts, which channel water from the roof to the ground. Ensure their capacity matches or exceeds the expected runoff. Use the chart provided to determine the number of extra downspouts needed for larger gutters.

By carefully considering gutter and downspout sizes, you’ll effectively manage rainwater, protecting your home from water damage.


Discovering the perfect gutter size is easier than ever with our guide. At Hepler Contracting, we’re committed to making the protection of your home a breeze! With our comprehensive instructions and calculations, you’ll confidently select the ideal gutters for your needs. Reach out to us at (412) 694-8785 to safeguard your property with new gutters in Pittsburgh. Don’t miss this opportunity to invest wisely in the right gutter size and protect your home from potential damages. Let’s work together to ensure efficient rainwater management!  

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