Roofers

Gutter Calculator

Estimate linear feet of gutters and number of downspouts needed for any roof.

Length of one eave (roofline edge)
Number of corner pieces needed
80
Linear Feet of Gutter
8
10-ft Sections
4
Downspouts
4
Corner Pieces
2
End Caps
8
Elbows
27
Hangers (@ 3 ft)

80 linear ft of gutter with 4 downspouts every 20 ft. Each downspout needs 2 elbows (top and bottom). Add 10% to material quantities for waste and cuts. Downspout extensions and splash blocks ordered separately.

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How to size gutters for your roof

Gutter sizing depends on two things: roof area draining into the gutter and your local rainfall intensity. Standard 5 inch K style gutters handle most residential roofs. For large roof areas or areas with heavy rainfall, 6 inch gutters or additional downspouts may be needed. This calculator helps you figure out the right gutter size based on your actual roof dimensions.

How many downspouts do I need?

The general rule is one downspout for every 20 to 30 linear feet of gutter. Each downspout handles the water from a section of the gutter, so spacing them evenly prevents overflow during heavy rain. Corner downspouts are common because they are easy to route. Make sure downspouts direct water at least 4 feet away from the foundation.

Gutter materials compared

Aluminum is the most popular because it is lightweight, does not rust, and is affordable. Copper looks great and lasts a long time but costs significantly more. Vinyl is the cheapest but does not hold up well in cold climates. Steel is strong but prone to rust if the coating gets damaged. For most residential jobs, aluminum is the go to choice.

Common Questions

How long do gutters last?

Aluminum gutters last 20 to 30 years. Copper gutters can go 50 years or more. Vinyl is the cheapest but only lasts 10 to 15 years and gets brittle in cold weather.

Should gutters go all the way around the house?

Not always. You need gutters on any eave where water drains toward the foundation, walkways, or landscaping you want to protect. Some sides of the house may not need them if the grading slopes away well.

What causes gutters to overflow?

Clogs from leaves and debris are the number one cause. Gutters that are too small for the roof area, not enough downspouts, or gutters that have lost their pitch also cause overflow.

Do I need gutter guards?

They help if you have a lot of trees dropping leaves. They do not eliminate cleaning completely but they cut it way down. Micro mesh guards work the best but cost the most.

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