Standard Gutter Sizes
Definition: The standard residential gutter in the US is 5-inch K-style aluminum with 2×3-inch downspouts. Larger or steeper roofs and heavy-rain areas get 6-inch K-style with 3×4-inch downspouts, which carries roughly twice the water. Half-round gutters come in the same 5- and 6-inch widths.
Gutter size is the width across the top of the gutter. Two sizes cover nearly every house.
5-inch K-style. The standard. K-style gutters have a flat back and a decorative front that looks like crown moulding, and hold more water than a half-round of the same width. Paired with 2×3-inch downspouts. One 2×3 downspout drains about 600 sq ft of roof in a heavy downpour.
6-inch K-style. For bigger roofs, steep roofs (they shed water faster, so it hits the gutter harder), long uninterrupted runs, roofs in high-rainfall areas, and anywhere a 5-inch gutter overflows at the corners. Paired with 3×4-inch downspouts, which drain about 1,200 sq ft each. The price difference is usually small next to the cost of the job.
Half-round. Round-bottomed gutters in 5 and 6 inches, common on older and historic houses and in copper. They hold less than K-style of the same width and need round downspouts.
Box gutters. Built into the roof edge or sized to a commercial building's specs; not something a homeowner picks from a chart.
What size do you need?
Start with the roof area each gutter run drains, not the whole house: a run catches only the slopes that drain into it. Then allow for pitch (steeper roofs need more capacity) and for your area's heaviest rainfall. As a rule of thumb, most single-family homes with ordinary roofs are fine with 5-inch gutters; a large or steep roof, or one in a region of intense storms, should get 6-inch. Our gutter takeoff also places a downspout at least every 35 feet of run, and adds more if the roof area behind a run calls for it.
Other measurements on a gutter quote
Gauge. Aluminum gutters come in 0.027 inch (standard) and 0.032 inch (heavier, dents less under ladders and ice). Seamless vs sectional: seamless gutters are formed on site to the full length of each run, with joints only at corners; sectional gutters join 10- or 20-foot lengths and leak at the seams sooner. Hangers: one every 24 inches is common, every 16 inches where snow and ice load the gutter.
Parts of a gutter system
- Gutter (trough): the run along the eave that catches the water.
- End caps: close each open end of a run.
- Inside and outside corners (miters): where runs turn around the house.
- Outlets (drops): the hole and collar where water leaves the gutter for the downspout.
- Downspout: the vertical pipe, 2×3 or 3×4 inches on houses.
- Elbows: bends at the top (to reach from the outlet back to the wall) and bottom (to point water away); most downspouts take three.
- Hangers: brackets that hold the gutter to the fascia, often hidden inside it.
- Extensions or splash blocks: carry water a few feet clear of the foundation.
- Gutter guards (leaf covers): optional screens or covers that keep leaves out.
Measure your own
The free gutter calculator traces your house from satellite, finds the eaves that need gutters, and counts runs, corners, end caps and downspouts for 5- or 6-inch gutters.