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Reviewed · Prices checked October 2026 · How we calculate

Gutter Calculator: How Many Gutters and Downspouts?

Enter the length of roof edge that gets gutters, how many separate runs and corners, and how tall the walls are. You get the main parts to buy: sections, connectors, downspouts, elbows, bands, hangers and end caps.

Inputs

Units
ft
ft
ft
Section length
Snow and ice
$

Parts list

Updates as you type
12sections

10 ft gutter sections for 120 ft of roof edge, with 4 downspouts

Gutter parts
Downspouts and outlets4
Downspout pipe, 10 ft pieces4
Downspout bands8
Section connectors10
Elbows12
Hangers60 (every 24 in)
End caps4
Inside and outside corners0 inside, 2 outside
Gutter sections at your price—

Also: gutter sealant for every seam and corner, screws for the hangers and bands, and any splash blocks or extensions at the bottom. Slope the gutter slightly toward each downspout, often about 1/4 in per 10 ft.

Show the math
Sections: 120 ft ÷ 10 ft = 12 → 12Downspouts: 120 ft ÷ 30 ft = 4 → 4 (at least one per run)Hangers: 1,440 in ÷ 24 in = 60

The price you type is used for this estimate only; it isn't saved.

How it works

The formula

sections = gutter length ÷ section length, rounded up
downspouts = gutter length ÷ spacing, rounded up, at least one per run
hangers = gutter length ÷ hanger spacing

Assumptions

  • Hangers every 24 in, or 18 in where snow and ice are heavy (Lowe's gutter installation guide).
  • Downspouts: advice runs from one every 20 ft to one every 40 ft of gutter, depending on roof size and rainfall; we default to 30 ft. Long roof slopes and heavy-rain areas need more.
  • Elbows: 3 per downspout (two to bring it back to the wall, one to turn it out at the ground), a rule of thumb. Downspout pipe comes in 10 ft pieces.
  • Each separate run takes 2 end caps; sections join with a connector; each 10 ft piece of downspout takes 2 bands (Lowe's guide). Corners are as you enter them.

Worked example

120 ft of gutter in 2 runs, 10 ft walls, a downspout every 30 ft

  1. 120 ÷ 10 = 12 sections
  2. 120 ÷ 30 = 4 downspouts, 4 pieces of pipe, 12 elbows
  3. 1,440 in ÷ 24 = 60 hangers, 4 end caps

Parts by gutter length

Gutter parts by length, 10 ft sections, a downspout every 30 ft, hangers every 24 in
GutterSectionsDownspoutsHangers
60 ft, 1 run6230
120 ft, 2 runs12460
160 ft, 2 runs16680
200 ft, 4 runs207100

Questions people ask

How many downspouts do I need?

Common advice is one every 20 to 40 ft of gutter, and at least one on every run. Big or steep roofs, and places with heavy downpours, need them closer.

How far apart should gutter hangers be?

About every 24 in, or 18 in where snow and ice load the gutters.

How do I measure for gutters?

Measure along every eave that sheds water, at the roof edge, and add the runs together. Count the corners where the gutter turns.

10 ft or 16 ft sections?

Longer sections mean fewer seams to leak, but they're harder to carry and hang. Seamless gutters are formed on site to any length by installers.