Gutters are sold and installed by the linear foot, so the whole job comes down to one question: how many feet of eave actually need one? Get that number right and the downspout count, hanger count, and cost all fall out of it.
Step 1: Measure the Eaves, Not the Whole Roofline
The eave is the horizontal edge of the roof where water runs off — not the gable end, where the roof forms a peak. On a simple gable roof, only the two long sides have eaves that need gutters; the triangular gable ends usually don't. On a hip roof, every side slopes down to an eave, so gutters typically run around the full perimeter.
| Roof Type | Sides Needing Gutter | Formula |
|---|---|---|
| Gable | 2 long eave sides | 2 × length |
| Hip | All 4 sides | 2 × (length + width) |
Step 2: Add a Waste Factor
Add about 5% to your total run length to cover corner pieces, seam overlaps, and cuts. Gutter comes in 10-ft sections for sectional/DIY installs, or is custom-formed on-site for seamless installs — either way, a small buffer avoids a second supply run.
Step 3: Space Your Downspouts
Plan on one downspout for roughly every 30–35 ft of gutter run, with a minimum of two per home even on smaller footprints — a single drain point risks overflow in a heavy storm. Each downspout also needs a vertical drop, typically about 10 ft per story from gutter to grade.
Step 4: Count Hangers
Hidden hangers (the brackets that hold the gutter to the fascia) are spaced every 2 ft on a standard install, tighter in regions with heavy snow load. Divide your total gutter length by 2 to get the hanger count.
Worked Example
A 50 ft × 30 ft home with a gable roof: 2 × 50 = 100 ft of eave, plus 5% waste = 105 ft of gutter. At one downspout per 32 ft, that's 4 downspouts. Hangers: 105 ÷ 2 ≈ 53. For a 1.5-story home, each downspout adds about 15 ft of vertical drop — 60 ft of downspout material on top of the 105 ft of gutter.
Choosing a Material
| Material | Price per Linear Foot | Lifespan |
|---|---|---|
| Vinyl | $3–5 | 10–20 years |
| Seamless Aluminum | $6–12 | 20–30 years |
| Galvanized Steel | $8–14 | 20–25 years |
| Copper | $25–45 | 50+ years |
Seamless aluminum is the most common residential choice — it resists rust, comes in many colors, and is custom-cut on-site so there are no seams for leaks to develop. Vinyl is the budget DIY option but gets brittle in cold climates over time.
5-Inch vs. 6-Inch Gutters
5-inch K-style gutters handle most residential roofs up to around 5,500 sq ft of roof area. 6-inch gutters drain roughly 40% more water and are worth the upgrade for steep roofs, large roof areas, or regions that see heavy downpours.
Frequently Asked Questions
How do I measure how much gutter I need? Measure the total length of every roof eave — the horizontal edges where water runs off. For a gable roof, that's usually the two long sides only; for a hip roof, all four sides.
How many downspouts do I need? One for every 30–35 ft of gutter run, with a minimum of two per home.
Does a hip roof need more gutter than a gable roof? Yes — a hip roof drains on all four sides, so gutters typically run around the full perimeter, while a gable roof only needs them on the two eave sides.
How much do new gutters cost installed? Materials run $3–45 per linear foot depending on the metal, and professional installation typically adds another $3–8 per foot on top.