Gutter Calculator

How to Measure Your Gutters

Walk each side of the house and measure the eave length (the horizontal bottom edge of the roof) in feet. Most houses have 2 to 4 eave runs — front, back, and possibly sides if the house has hip roofs. Enter each run separately; the calculator adds them. For each run, figure one downspout per 35 linear feet for 5-inch gutter, 50 feet for 6-inch, or 60 feet for 7-inch. A typical 2-story home has 120 to 200 linear feet of gutter and 4 to 8 downspouts.

Which Size Gutter to Pick

For most single-story and modest two-story homes in average-rainfall climates, 5-inch K-style is enough. Upgrade to 6-inch for any of: roof area over 2,000 sq ft draining to one gutter run, roof pitch over 6:12 (steeper pitches shed water faster into the gutter), heavy rainfall climates (above 50 inches per year), or long eave runs over 40 feet. 7-inch is for commercial buildings and exceptional cases. Larger gutters also handle leaves better because debris does not block flow as easily, which is a real benefit in wooded lots.

Seamless vs Sectional Gutters

Seamless gutters are extruded on site by a gutter machine to the exact length of each run, leaving only miters at corners and end caps. They leak less, last longer, and cost about the same installed as sectional. Sectional gutters are 10-foot aluminum sections joined with connectors and sealed. They are DIY-friendly but every joint is a potential leak point. For a first installation, pay a pro for seamless; for a small addition or shed, DIY sectional is fine.

Slope and Drainage

Gutters should slope 1/4 inch per 10 feet toward the downspout. Longer runs (over 40 feet) slope from the center down to a downspout at each end. Too much slope looks crooked; too little and water sits in the gutter, causing sag and algae. Downspouts should discharge at least 4 feet from the foundation — use splash blocks, extensions, or underground drain tiles connected to a pop-up emitter in the lawn. Never discharge gutter water directly at the foundation.

Frequently Asked Questions

How often should I clean gutters?

Twice a year — spring and fall — or more if your home is under trees.

Are gutter guards worth it?

Yes, in wooded areas. Micromesh designs are best; foam inserts trap debris inside the gutter.

Can I add gutters to a porch?

Yes — small porches usually take 10 to 20 linear feet with a single downspout.

Do I need gutters on a metal roof?

Yes — metal sheds more water, faster, than asphalt, so gutters are still important for foundation protection.

How long do aluminum gutters last?

20 to 25 years with maintenance. Copper gutters last 50+ years.