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This gutter calculator builds a parts list for a rain gutter installation. Enter the total eave length, the number of separate runs, corners and the downspout height, and it estimates gutter sections, downspouts, elbows, hangers, end caps and outlets.
How to Use the Gutter Calculator
- Measure every eave that needs a gutter and add the lengths together.
- Count the separate gutter runs (each run has two ends).
- Count inside and outside corners.
- Measure the height from the eave to the ground for downspouts.
Rules of Thumb Used
- One downspout for every 30–40 ft of gutter (35 ft used), with at least one per run.
- A hanger every 24 in, or every 18 in where heavy snow and ice are common.
- Three elbows per downspout: two at the top to reach the wall and one at the bottom.
- Two end caps per run and one outlet per downspout.
Example
A house with 120 ft of eaves in four runs needs 12 sections of 10 ft gutter, 4 downspouts with 40 ft of downspout pipe, 12 elbows, 64 hangers and 8 end caps.
Gutter Sizes
| Gutter | Downspout | Typical use |
|---|---|---|
| 5 in K-style | 2 × 3 in | Most homes |
| 6 in K-style | 3 × 4 in | Large or steep roofs, heavy rainfall |
| 5–6 in half-round | 3 in round | Historic and traditional homes |
Installation Tips
- Slope gutters about ¼ in toward the downspout for every 10 ft.
- Runs over 40 ft are usually pitched from the middle to downspouts at both ends.
- Seal every joint and end cap with gutter sealant.
- Direct downspouts at least 4–6 ft away from the foundation.
Replacing the roof too? Try the roof replacement cost calculator.
Frequently Asked Questions
How many downspouts do I need?
As a rule of thumb, one downspout for every 30–40 ft of gutter, and at least one for every separate run.
How far apart should gutter hangers be?
About every 24 in, or every 18 in in areas with heavy snow.
How much slope should gutters have?
About ¼ in of fall for every 10 ft of gutter toward the downspout.
What size gutters do I need?
5 in K-style gutters suit most homes. Large, steep roofs or areas with intense rainfall may need 6 in gutters and larger downspouts.
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