Gutter Calculator
Add up your roof's eaves and this works out the gutter to buy, plus the downspouts and hangers to hold it.
Gutter (10-ft sections)
12sections
- Downspouts
- 4 downspouts
- Hangers
- 61 hangers
- Total run
- 120 linear ft
How it’s calculated
Gutter sections = ⌈ total run ÷ 10 ⌉ — sectional K-style gutter is sold in 10-foot lengths (seamless gutter is roll-formed to the run, so go by the total linear feet). Downspouts = ⌈ run ÷ spacing ⌉, one per ~30–40 ft. Hangers = ⌈ run ÷ spacing ⌉ + 1 — a bracket at each end of the run — spaced about every 24 inches, tighter (16–18 in) in snow country.
Worked example
120 ft of eaves: ⌈120 ÷ 10⌉ = 12 sections; ⌈120 ÷ 35⌉ = 4 downspouts; at 24-in hanger spacing, ⌈(120 × 12) ÷ 24⌉ + 1 = 60 + 1 = 61 hangers.
FAQs
- How many downspouts do I need?
- Plan on one per about 30–40 feet of gutter — roughly one per 600–800 sq ft of roof drained. Long runs and big roofs need more so water doesn't overrun the gutter in a heavy rain.
- How far apart should gutter hangers go?
- About every 24 inches, with a hanger at each end of every run (so it's one more than the number of gaps). Tighten to 16–18 inches in regions with snow and ice — a loaded gutter is what pulls away from the fascia.
- Should I get 5-inch or 6-inch gutter?
- 5-inch K-style handles most homes; step up to 6-inch (with 3×4-inch downspouts) for large or steep roofs that shed a lot of water fast. Capacity is gated by the downspout as much as the trough, so size them together.
Sources
- Sectional gutter sold in 10-ft lengths (seamless = total linear ft). Conventions: a downspout per ~30–40 ft of run (~600–800 sq ft of roof); a hanger every ~24 in plus one for both ends, tighter in snow. Verify against local rainfall/code.