About ExteriorCalcs
ExteriorCalcs is an independent project with one goal: to gather the everyday calculations homeowners, DIYers and contractors reach for when planning exterior work — roof pitch and area, shingle and material quantities, roof-replacement cost math, gutters, siding, windows and the attic — in one focused, free, no-signup hub with transparent formulas.
Who is behind it
Author and curator
To be clear about credentials: I am the author and curator of this site — not a licensed roofing contractor, general contractor or building inspector. What I bring is relevant and real: building deterministic online calculators (open-source Python projects) and engineering training, i.e. rigor on geometry, trigonometry, drainage hydraulics and heat-flow math. That is what it takes to curate a hub of calculators: transparent method, correct formulas, cited constants and worked examples.
Our principle: transparent & durably correct
Every calculator shows its formula, a worked example and a reference table. The tools rest only on timeless construction math and stable industry/code constants: 1 roofing square = 100 sq ft, 3 bundles per square, SMACNA-derived K-style gutter capacities, IRC egress and attic-ventilation minimums (cited with their 2021 edition; local code prevails), and R-per-inch of insulation materials. There are deliberately no material prices, no labor-rate database and no live feeds — the cost tools use the price you enter from your own quotes — so the results stay valid over time.
Correctness is checked against known reference values (see the numeric self-check). The formulas and their sources are documented under Sources & formulas. All results are planning estimates: measure your roof, get real written quotes, use fall protection or hire a licensed pro, and defer code questions to your local building official. Questions? Use the contact page.