Gutter Calculator
Measure the eave line before you order gutter.
Gutter Calculator
Gutter length = edge run x (1 + waste); hangers = ceiling(edge run in inches / spacing) + 1; pipe = downspouts x length each.
Calculated instantly
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What This Calculator Does
The Gutter Calculator turns the length of the eave line into an order list: gutter in linear feet, hangers at your spacing, downspout pipe, and the number of 10 ft sections. It is a takeoff tool, not a gutter-sizing tool, so it does not guess a 5 in or 6 in profile from the roof area.
How It Works
Gutter is ordered by linear foot along the eave. The tool adds your waste allowance, then counts hangers by converting the run to inches, dividing by the hanger spacing, rounding up, and adding one for the end. Downspout pipe is the number of downspouts multiplied by their drop length, and the total is divided into 10 ft sections so you can match stock lengths and couplers.
Example
A house with 120 ft of eave, 4 downspouts dropping 10 ft each, hangers at 24 in, and 5 percent waste needs 126 ft of gutter, ceil(1440 / 24) + 1 = 61 hangers, 40 ft of downspout pipe, 166 ft of material in total, and 17 sections at 10 ft.
Formula
edge run x (1 + waste / 100)ceiling(edge run in inches / hanger spacing) + 1number of downspouts x drop length eachceiling(total gutter and pipe / 10)Reading the Results
Gutter length to buy
Eave run plus waste. Waste covers corners, outlets, and cut ends; add more for a complex roofline with many inside and outside corners.
Hangers
Count based on your spacing plus one end hanger. Hidden hangers, spikes and ferrules, and snow guards may change the count and fixing pattern.
10 ft sections
A shopping aid for sectional gutter sold in 10 ft lengths. Seamless gutter is ordered as one continuous run and does not use this number.
Sources and References
International Residential Code - Chapter 9, Roof Assemblies
Roof drainage and gutter requirements
Sets the code framework for drainage, but the adopted edition and local amendments control.
SMACNA Architectural Sheet Metal Manual
Gutter sizing and downspout capacity tables
The industry reference for sizing a gutter profile from roof area and rainfall intensity, which this takeoff tool does not do.
References identify the method or data behind this calculator. Where a standard or tariff changes, the current edition applies, and the assumptions stated above take precedence over a remembered figure.
Frequently Asked Questions
How do I know whether I need 5 in or 6 in gutters?
Size the profile from the roof area draining to each run and the local rainfall intensity, using a gutter sizing table or the manufacturer guidance. A long run with a steep roof and one downspout may need 6 in even on a modest house. This calculator only measures the run you have chosen.
How far apart should gutter hangers be?
Twenty-four inches is common for mild conditions. Cold climates with snow and ice, heavy rainfall, or metal gutters often need 12-18 in, and the manufacturer instructions override any rule of thumb. Closer spacing also helps a gutter hold its slope under load.
How many downspouts does a gutter run need?
One downspout per 30-40 ft of run is a common starting point, but the limit is the roof area and rainfall intensity, not length alone. Each downspout must also discharge far enough from the foundation, and the outlet should not create a trip hazard or a slope back toward the house.
Does the calculator include elbows, outlets, and end caps?
No. Those are counted per corner and per downspout, not per foot. Add one outlet per downspout, two end caps per run, and elbows for every change of direction, then check the manufacturer parts list for the profile you are installing.
What slope should a gutter have?
A common target is about 1/4 in of fall per 10 ft toward the downspout, but follow the manufacturer and local practice. The calculator does not adjust length for slope because the difference is small compared with waste and corner allowances.