Gutter Calculator
The eave take-off: run, downspouts, drop footage, hangers and elbows, with the installed-band pricing on one card.
Gutter Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Rectangular-plan eaves — bays and turrets add their own runs.
- No rainfall-intensity sizing; the 5-in/6-in doctrine card is screening.
- Leaf guards and fascia repair priced separately.
In short: A 150-ft run at 35-ft spacing on a 10-ft wall: 5 downspouts, 70 ft of downspout drop, 75 hidden hangers, 15 elbows and 17 ten-foot sticks — $1,350.00 installed at the $9 aluminum mid-band. One downspout per 30-40 ft is the whole law; the rest is counting.
Formula
downspouts = ⌈run ÷ spacing⌉, min 1 per run
drop = downspouts × (wall + 4 ft)
hangers = ⌈run × 12 ÷ 24⌉ — elbows = 3 × downspouts
installed = run × $/ft
[('30-40 ft', 'the downspout spacing rule; 50 ft is the practical run ceiling'), ('24 in', 'hanger spacing, standard; 18 in snow, 12 in extreme'), ('4,500 ft²', 'roof area a 5-in K-style carries at 1 in/hr'), ('$6-12', 'installed band, vinyl to steel; copper $18-35')]
Worked Example
- Measure every eave run that receives gutter; add to linear feet.
- Place downspouts at 30-40 ft; count them.
- Add wall height plus 4 ft per downspout for the drop.
- Hang at 24 in; plan three elbows per drop.
- Price the run at your material's installed band.
150 ft at 35-ft spacing, 10-ft wall, aluminum at $9: 5 downspouts, 70 ft of drop, 75 hangers, 15 elbows, 17 10-ft sticks — $1,350.00 installed.
Strengths & Limits Of This Model
Where this engine is strong
- Full parts take-off, not just a run length
- Installed bands by material, free-entry
- The 1,400 ft²-per-downspout upsize trigger on a card
Where it stops
- No roof-area drainage model
- Sectional waste fixed at 10%
Practical Use Cases
Replacements
Whole-perimeter take-offs before quotes.
New construction
Run, drop and hanger schedules.
Seamless orders
Linear feet for the fabricator.
DIY sectional
10-ft stick counts with cut waste.
Material shopping
Aluminum vs steel vs copper bands.
Methodology & Editorial Standards
The take-off is counting, not estimating: downspouts by the 30-40 ft rule (ceil of run ÷ spacing, one minimum), drop footage at wall + 4 ft each, hangers at 24-in centers, three elbows per drop, and 10-ft sticks at 10% cut waste. Cost is the free-entry installed rate times the run — the rate chips are researched band midpoints, not assertions. Runs ≤ 0 and spacings outside 10-100 ft are refused.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Gutter Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How many downspouts do I need?
One per 30-40 linear feet of gutter is the working rule — 150 ft gets five at 35-ft spacing. Fewer and the gutter overflows in hard rain; past 50 ft on any single run, add relief.
How far apart should gutter hangers be?
Every 24 inches in standard climates, tightening to 18 in in heavy-snow regions and 12 in under extreme ground-snow loads. Spaced wider, the run sags within a couple of seasons.
5-inch or 6-inch gutters?
5-inch K-style carries about 4,500 ft² of roof at a 1-in/hr rain; 6-inch about 7,800. The practical trigger: when one downspout would serve more than 1,400 ft² of roof, upsize to 6-inch with 3×4 downspouts.
How much does gutter installation cost per foot?
Installed bands: vinyl $4-8, aluminum $6-12 (the national default), galvanized steel $8-14, copper $18-35. K-style is the base price; half-round adds roughly 20%.
How long should each downspout be?
Wall height plus about 4 feet of ground extension that carries water away from the foundation. A 10-ft wall means a 14-ft drop, typically one 10-ft stick plus an offcut.
Do gutters need slope?
Yes — about 1/8 inch of fall per foot toward the downspout outlet. A level gutter holds water; a graded one drains it.
Seamless or sectional?
Sectional ships in 10-ft sticks and seals at every joint; seamless is roll-formed to your run length on site and priced by the linear foot. Long runs and heavy regimes favor seamless.
What about gutter guards?
Guards run $3-10 per linear foot installed and pay for themselves where trees overhang the roofline — they cut cleaning frequency, they do not change any count on this page.