About ChimneyCalcs
ChimneyCalcs is an independent project with one goal: to gather the everyday calculations homeowners, DIYers and small masons or sweeps reach for around a chimney and its hearth appliance — flue and liner sizing, the chimney-height and draft geometry, and repair, relining, sweep, inspection and installation cost — in one focused, free, no-signup hub with transparent formulas, so you can size a flue, budget a job and sanity-check a sweep’s or a mason’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 chimney sweep, a mason 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). Chimney and flue sizing is plane geometry (a flue’s cross-section is 1/10 to 1/12 of the fireplace opening; the area of a circle is A = π·(d/2)²; a round diameter is d = 2·√(A/π); the 3-2-10 height rule is a max() of two clearances; a liner’s cross-section ≥ the appliance outlet) and cost is a quantity × unit-price sum (cost = materials/linear-foot + labor + access, ×(1 + contingency)) — the same rigorous arithmetic I apply in systems and electronics, so the math of these calculators is squarely in my competence, while creosote, chimney fire, carbon monoxide, structural judgement and code compliance are explicitly deferred to CSIA-certified sweeps, licensed masons, NFPA 211 and local code.
Our principle: transparent & durably correct
Every calculator shows its formula, a worked example and a reference table. The tools rest only on timeless flue geometry and cost arithmetic and stable, labeled conventions (the 1/10–1/12 flue rule, standard clay-tile sizes, liner-by-appliance, creosote stages, NFPA 211 inspection levels, clearances, cost bands). There are deliberately no live material or labor rates, no regional cost databases, no product catalog and no sweep or mason 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, which cites public standards bodies such as NFPA and the Chimney Safety Institute of America. All results are planning estimates and sizing / draft guides: get itemized written quotes from a CSIA-certified sweep and a licensed, insured mason, confirm your exact flue and opening dimensions, and follow NFPA 211, the appliance manufacturer’s instructions and local code. Combustion, chimney fire, carbon monoxide, structural and code judgement are out of scope. Questions? Use the contact page.