Gutter Size Calculator

What size gutter do I need?

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5-inchK-style

Roof area × pitch factor × rainfall intensity, compared with published K-style ratings of about 5,520 sq ft for 5 inch and 7,960 sq ft for 6 inch. Treat as typical and check your local rainfall figure.

5-inch K-styleAdjusted load 4,950 sq ft90% of rating
Pitch factor1.1
Adjusted area4,950 sq ft
Rating used5,520 sq ft

Check whether a 5 inch or 6 inch K-style gutter fits your roof area, pitch and rainfall.

How it works

Roof area × pitch factor × peak rainfall gives an adjusted area, compared with the published K-style ratings.

Before you order

  • Use the peak short-storm rainfall for your area. Yearly totals do not size gutters.
  • Valleys pour extra water at one spot, so size for those runs.
  • A larger gutter needs larger downspouts to match.

Common questions

What size gutter is standard?

5 inch K-style is most common on houses, with 6 inch for larger roofs.

Does roof pitch affect gutter size?

Yes. Steeper roofs catch more wind-driven rain, so pitch factor rises with slope.