About GutterCalcs
GutterCalcs is an independent project with one goal: to gather the everyday calculations homeowners, DIYers and small contractors reach for when gutters go up — sizing & quantity, cost estimators, gutter guards, downspouts & drainage, cleaning, and materials & types — in one focused, free, no-signup hub with transparent formulas, so you can budget a gutter project and sanity-check a contractor’s quote.
Who is behind it
Author and curator
To be clear about credentials: I am the author and curator of this site — not a licensed gutter or roofing contractor, a drainage engineer or any trade professional, and I claim no trade credential. What I bring is relevant and real: building deterministic online calculators (open-source Python projects) and electronic-engineering training (Systems Theory, Sapienza University of Rome). Gutter sizing is a hydraulics problem — effective roof catchment area × rainfall intensity → the flow capacity a gutter and downspout size must carry — the same flow-vs-capacity reasoning I apply in systems and electronics, so the math of these calculators is squarely in my competence, while gutter-contractor judgement (installation quality, fascia condition, height/access, local code) is explicitly deferred to licensed pros and manufacturer data.
Our principle: transparent & durably correct
Every calculator shows its formula, a worked example and a reference table. The tools rest only on timeless drainage geometry (linear feet = Σ eave runs; effective area = footprint × pitch factor; the smallest size whose drainage area ≥ that area; downspouts / sections / hangers by ceil; rainwater gallons = area × inches × 0.6234 × runoff; cost = quantity × your $/unit + labor + add-ons, ×(1 + contingency)) and stable, labeled conventions (roof-pitch multipliers, US rainfall intensity, drainage area per gutter size, downspout capacity, hanger spacing, cost bands). There are deliberately no live material or labor prices, no regional cost indexes, no product catalog and no contractor directory — cost tools use the prices you enter — so the results stay valid over time.
Correctness is checked against known reference values (see the methodology and the numeric self-check). The formulas and their basis are documented under Sources & formulas. All results are planning estimates and material-quantity / sizing guides: get itemized written quotes from licensed, insured gutter contractors, measure your eave runs and confirm capacity, spacing and coverage against the exact product, and order a little extra (~5–10%) for corners, waste and slope. Structural roof-load, roofing, code certification and foundation/yard drainage are out of scope and are for local code and a certified professional. Questions? Use the contact page.