How many gutter sections do I need?

Add up the eave length you will gutter, add about 5% for cuts and divide by 10 ft, rounding up. 9 sections cover 80 ft with 5% extra (84 ft ÷ 10 = 8.4). Seamless gutter is made on site to length, so order the total feet instead.

How far apart should gutter hangers be?

Manufacturers of hidden hangers commonly call for one about every 24 in of gutter, and closer (about 18 in) where snow and ice load the gutter. Check the instructions for the gutter and hanger you buy, as spacing varies by product.

How many downspouts do I need?

A common rule of thumb is one downspout per 30 to 40 ft of gutter, closer (about 20 ft) on steep roofs or in heavy rain, and at least one per run. For 80 ft in two runs at one per 30 ft that is 3. This is a typical spacing, not a sizing: the right number depends on the roof area draining to each downspout, your local rainfall intensity and the gutter and downspout size. The calculator shows the roof area per downspout; compare it with the capacity chart from your gutter maker or use SMACNA’s sizing calculator.

Should I use 5 in or 6 in gutters?

5 in K-style gutters are the usual size on houses; 6 in gutters carry more water and suit large or steep roofs, long runs and heavy-rain areas. This calculator does not compute their capacity, because the published tables depend on rainfall intensity and the gutter profile: use the chart from your gutter manufacturer or SMACNA’s sizing calculator.

How much slope should a gutter have?

About 1/4 in of fall per 10 ft toward the downspout is the figure commonly cited, so a 40 ft run drops about 1 in. The table on this page lists the drop by run length; the slope calculator finds the drop over any length.

How many elbows do I need per downspout?

Three is typical: two at the top to jog the pipe in from the eave to the wall, and one at the bottom to turn the water away from the house. 3 downspouts give 9 elbows. A downspout that drops straight from a gutter over a wall with no eave to cross needs fewer, and a bottom run into a drain pipe needs none.

How many end caps and corners do I need?

Every open end of a run needs an end cap, 2 per run. A gutter that wraps a corner of the house joins itself with a corner piece instead: an outside corner where the house turns out, an inside corner where two eaves meet in a concave angle. Count them on your plan and enter them.

Does this count sealant, connectors and straps?

No. Sealant, slip-joint connectors, downspout straps and screws vary by product and installer, and no published coverage figure supports a count, so check your gutter system’s parts list and add them to your order.

Gutter and Downspout Calculator: How Many Sections and Downspouts?

A house with 80 ft of eave to gutter (the two long sides of a 40 × 30 ft house) needs 9 sections of 10 ft gutter (80 ft plus 5% for cuts), 42 hangers set 24 in apart, 4 end caps, 3 downspouts with 3 outlets and 9 elbows. Sections = eave length ÷ 10 ft, rounded up; hangers = eave length ÷ hanger spacing; downspouts = about one per 30 ft (a typical rule of thumb, not a sized figure).

Figures based on the sources listed belowUpdated 2026-10-04How we calculate

Total eave length to gutter

Roof run, eave to ridge (flat)

Extra gutter

Sectional: cuts and scrap (5%)Exact (0%)Custom

Separate runs

Stretches of gutter with two open ends, each closed by an end cap. A gutter that wraps a corner is one run.

Inside corners

Where two eaves meet at a concave (inside) corner of the house, as in an L or a T.

Outside corners

Where the gutter turns a convex (outside) corner of the house.

Hanger spacingManufacturers commonly call for a hanger about every 24 in; closer spacing is used where snow and ice load the gutter. Follow your gutter’s instructions.

Gutter length per downspoutA common rule of thumb is one downspout per 30 to 40 ft of gutter, closer for steep roofs. Every run gets at least one.

Downspout height (ft)

From the gutter down to the ground or the splash block.

Roof pitch (rise per 12 in of run, x/12)

Used only to turn the flat roof area into the sloped area that sheds rain. Use the slope calculator if you only have an angle or a percent.

Price per section (optional)

Buy 9 sections

80 linear ft + 5% waste = 84 linear ft

Seamless gutter, if you order by the foot: 84 ft
Hangers (every 24 in): 42 hangers
End caps (2 per run): 4 end caps
Inside corners: 0 corners
Outside corners: 0 corners
Downspouts: 3 downspouts (each about 10 ft)
Outlets (1 per downspout): 3 outlets
Elbows (3 per downspout, typical): 9 elbows
Roof area drained per downspout: 447 sq ft, compare with your gutter maker’s chart

Low

$72.00

Expected

$108.00

High

$198.00

Includes 4 linear ft waste

How this number is calculated

80 linear ft + 5% waste = 84 linear ft ÷ 10 linear ft per section = 9 sections

Shopping list

Aluminum gutter hangers (hidden, with screws)
Gutter end caps
Gutter sealant
Downspout elbows
Downspout extension
Gutter guards

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Gutter parts by house size

Two runs, 5% extra for cuts, hangers 24 in or 18 in apart, and downspouts at one per 40, 30 or 20 ft, worked by this calculator. Eave length is the total to be guttered: a 40 × 30 ft gable house with gutters on the long sides is 80 ft. Downspout counts are rule-of-thumb figures, not sized for your rainfall.
Eave length	10 ft sections	Hangers, 24 in	Hangers, 18 in	Downspouts, 1 per 40 ft	Downspouts, 1 per 30 ft	Downspouts, 1 per 20 ft
40 ft	5	22	29	2	2	2
60 ft	7	32	42	2	2	3
80 ft	9	42	56	2	3	4
100 ft	11	52	69	3	4	5
120 ft	13	62	82	3	4	6
160 ft	17	82	109	4	6	8
200 ft	21	102	136	5	7	10

Gutter fall by run length

About 1/4 in of drop per 10 ft of run toward the downspout (a commonly cited figure; follow your gutter’s instructions). A run with a downspout at each end can slope down from the middle.
Run length	Drop over the run	Drop in mm
10 ft	0.25 in	6.4 mm
20 ft	0.5 in	12.7 mm
30 ft	0.75 in	19 mm
40 ft	1 in	25.4 mm
50 ft	1.25 in	31.8 mm
60 ft	1.5 in	38.1 mm

Methodology & assumptions

The eave lengths you will gutter are added up into one number. Sections = that length × (1 + extra) ÷ 10 ft, rounded up; for seamless gutter, which is formed on site in one piece, order the length with the extra (shown under the result). Hangers = length × 12 ÷ spacing, rounded up, plus one for each run so every run ends on a hanger. Spacing is 24 in, the figure commonly given in manufacturer instructions, or 18 in for snow and ice; confirm it against the instructions for the gutter you buy. End caps are 2 per separate run, so a gutter that wraps a corner is one run; inside and outside corners are the counts you enter, since they depend on the shape of the house. Downspouts = the larger of one per run and the length ÷ the spacing you choose (40, 30 or 20 ft), rounded up. The 30 to 40 ft figure is a common installer rule of thumb (an estimate); steeper roofs and heavy rain call for closer spacing. Each downspout gets one outlet and, as is typical, three elbows (two at the top to offset the pipe from the eave to the wall, one at the bottom to kick the water away). That elbow count is a typical figure: a straight drop with no eave offset takes fewer. The roof area per downspout is the flat roof area (eave length × the run from eave to ridge) × the pitch factor √(1 + (rise ÷ 12)²), the same one the shingles calculator uses, ÷ the number of downspouts. It is shown so you can compare it with the capacity chart for your gutter; the calculator does not size the gutter itself, because the published capacity tables (SMACNA, Architectural Sheet Metal Manual) depend on the rainfall intensity for your area and on the gutter profile, and we could not check specific 5 in and 6 in figures against the source. Sealant, connectors and straps are not counted. The metric toggle shows lengths in m.

Hunker, “Recommended rain gutter slope”: about 1/4 in of fall per 10 ft of gutter (secondary source, typical figure)
Green Building Advisor, “Pitch for gutters?”: discussion of gutter slope (secondary source)
Amerimax 5 in aluminum hidden gutter hanger listing (Lowe’s): hangers about every 24 in of gutter
Gutterall, 4K no screw K style gutter hanger product page: hanger spacing no more than 24 in, closer in snow and ice country
LeafFilter, “How many downspouts do I need”: one downspout per 30 to 40 ft of gutter, closer on steeper roofs (installer rule of thumb; an estimate, not a sizing result)
SMACNA, Downspout & Gutter Sizing Calculator (based on the Architectural Sheet Metal Manual): to size a gutter and downspout for your rainfall intensity
Three elbows per downspout (two at the top, one at the bottom) is a common installer count: a typical figure, not from a published standard
Typical US retail prices for 10 ft aluminum K-style gutter sections, 2026 (unverified estimate)

How to calculate gutter materials

Measure the eaves. Add up the length of every eave you will gutter. Note how many separate runs there are and count the inside and outside corners.
Count the gutter. Add about 5% for cuts and divide by 10 ft, rounding up, or order the total feet for seamless gutter.
Count the hangers. Divide the gutter length in inches by the hanger spacing (24 in usual, 18 in in snow country), round up and add one per run.
Add the end caps. Two end caps for each separate run.
Place the downspouts. About one per 30 to 40 ft of gutter and at least one per run, closer on steep roofs or in heavy rain. Add an outlet each and about three elbows each.

Worked examples

Project	Result
40 × 30 ft gable house, gutters on the two long sides (80 ft), 24 in hangers, one downspout per 30 ft	80 linear ft + 5% extra → 9 sections, 42 hangers, 4 end caps, 3 downspouts, 9 elbows
Gutter all the way round a 40 × 30 ft hip-roof house (140 ft, one run, 4 outside corners) in snow country, 18 in hangers, one downspout per 40 ft	140 linear ft + 5% extra → 15 sections, 95 hangers, 2 end caps, 4 downspouts, 12 elbows
Three short runs totalling 60 ft with no extra, one downspout per 20 ft	60 linear ft + 0% extra → 6 sections, 33 hangers, 6 end caps, 3 downspouts, 9 elbows

Frequently asked questions

How many gutter sections do I need?: Add up the eave length you will gutter, add about 5% for cuts and divide by 10 ft, rounding up. 9 sections cover 80 ft with 5% extra (84 ft ÷ 10 = 8.4). Seamless gutter is made on site to length, so order the total feet instead.
How far apart should gutter hangers be?: Manufacturers of hidden hangers commonly call for one about every 24 in of gutter, and closer (about 18 in) where snow and ice load the gutter. Check the instructions for the gutter and hanger you buy, as spacing varies by product.
How many downspouts do I need?: A common rule of thumb is one downspout per 30 to 40 ft of gutter, closer (about 20 ft) on steep roofs or in heavy rain, and at least one per run. For 80 ft in two runs at one per 30 ft that is 3. This is a typical spacing, not a sizing: the right number depends on the roof area draining to each downspout, your local rainfall intensity and the gutter and downspout size. The calculator shows the roof area per downspout; compare it with the capacity chart from your gutter maker or use SMACNA’s sizing calculator.
Should I use 5 in or 6 in gutters?: 5 in K-style gutters are the usual size on houses; 6 in gutters carry more water and suit large or steep roofs, long runs and heavy-rain areas. This calculator does not compute their capacity, because the published tables depend on rainfall intensity and the gutter profile: use the chart from your gutter manufacturer or SMACNA’s sizing calculator.
How much slope should a gutter have?: About 1/4 in of fall per 10 ft toward the downspout is the figure commonly cited, so a 40 ft run drops about 1 in. The table on this page lists the drop by run length; the slope calculator finds the drop over any length.
How many elbows do I need per downspout?: Three is typical: two at the top to jog the pipe in from the eave to the wall, and one at the bottom to turn the water away from the house. 3 downspouts give 9 elbows. A downspout that drops straight from a gutter over a wall with no eave to cross needs fewer, and a bottom run into a drain pipe needs none.
How many end caps and corners do I need?: Every open end of a run needs an end cap, 2 per run. A gutter that wraps a corner of the house joins itself with a corner piece instead: an outside corner where the house turns out, an inside corner where two eaves meet in a concave angle. Count them on your plan and enter them.
Does this count sealant, connectors and straps?: No. Sealant, slip-joint connectors, downspout straps and screws vary by product and installer, and no published coverage figure supports a count, so check your gutter system’s parts list and add them to your order.

Handy tools

Slope Calculator: Gutters are hung with a slight fall toward the downspout, commonly about 1/4 in per 10 ft: find the drop over your run.