Roofing & Exterior
Gutter Calculator
Plan the materials for new gutters. Enter the length of each eave, and this gutter calculator counts the gutter sections, hangers, downspouts, elbows and end caps you need, with an optional cost. It is a material list, not a drainage sizing.
Result
Enter your measurements and press Calculate. What to buy, the working and the cost will appear here.
How to use the gutter calculator
- Measure each eave run where gutters will hang, and add a row per run (or use How many for matching runs).
- Enter the section length you are buying (10 ft is standard) and the hanger spacing.
- Set the downspout spacing and length (about 10 ft per story) and the number of corners.
- Add prices and press Calculate.
How gutter materials are counted
- Sections: each run, plus a little for overlaps, cut from your section length.
- Hangers: run length ÷ spacing, plus one, for each run.
- Downspouts: at least one per run, more on long runs at the spacing you set.
- Elbows: about three per downspout (two to bring it back to the wall, one at the bottom).
- End caps: two per run.
Worked example: front and back eaves
A house has two 42 ft eaves, front and back, with 10 ft gutter sections at $12, downspouts at $14 and hangers at $2.50:
- Run 1: 42 ft × 2, 5% extra for overlaps
- Sections: cut list of each run into 10 ft sections = 9
- Hangers: each run ÷ 2 ft spacing, + 1 = 44
- Downspouts: each run ÷ 35 ft, at least 1 per run = 4
Gutter sections: 9 sections of 10 ft; Downspouts: 4; Hangers: 44; Estimated cost: $274.00. Open this example in the calculator.
Planning gutters
- Slope: gutters are usually pitched toward the downspout, commonly about 1/4 in per 10 ft.
- Long runs over about 40 ft are often split to slope both ways to two downspouts.
- Hangers every 24 in for most homes, closer where snow and ice load the gutters.
- Seamless gutters are formed on site from a coil in one piece per run, so you pay per foot instead of per section.
- Leaf guards and splash blocks or extensions at the bottom of each downspout keep water away from the foundation.
What this calculator does not do
It counts materials for the runs you enter. It does not size gutters or downspouts for your roof area and local rainfall intensity. For steep roofs, large roof areas or heavy-rain regions, follow local practice or ask a gutter installer.
Assumptions and limitations
- Each run has two ends; runs that wrap a corner use the corner count you enter.
- Elbows are estimated at three per downspout.
- Sealant, screws, rivets and brackets for downspouts are not counted.
Gutter questions
How many downspouts do I need?
At least one per gutter run, and commonly one for every 30–40 ft of gutter. Large roof areas and heavy rain call for more.
How far apart should gutter hangers be?
Usually every 24 in, and as close as 12–18 in in areas with heavy snow.
How much gutter do I need?
Measure the length of every eave that will carry a gutter and add them up. Add a few percent for overlaps if you are joining sections.
Formulas, unit conversions and default values are explained on our methodology page. Results are estimates; check manufacturer data and local codes before you buy or build.