DuctSizingCalculator.com is a small, independently run tool. We read every message.
General questions, corrections, or feedback: [email protected]
The calculator's formulas — the equal-friction equation, the velocity formula, and the round-to-rectangular conversion — are documented in full on the How This Calculator Works page. If a result looks wrong, email us the CFM, friction rate (or target velocity), and the size you got, and we'll check it against the formulas directly.
Ideas for additional sizing modes, materials, or reference tables are welcome at the same address — this is an actively maintained tool, not a set-and-forget page.
Nothing you enter into the calculator — CFM, friction rate, duct sizes — is sent to us or stored anywhere outside your own browser. See the privacy policy for the full picture.