Update log

New tools, coefficient improvements and methodology changes — so you know when a number might differ from last time.

1. Oct 22, 2026Improvement

   Equivalent length, velocity limits and material guidance reviewed

   Expanded equivalent-length definitions and formulas using reported search queries; corrected its example from the calculator. Aligned velocity guidance with tool screening bands, qualified noise and code claims, and added calculated material comparisons, installation cautions, source references and related calculator links.

2. Oct 18, 2026Improvement

   Worked examples added to six calculator pages

   The CFM/Velocity/Area, Fan Static Pressure, Equivalent Length, Unit Converter, Duct Weight and Rectangular-to-Round converters each gained a fully worked numerical example with step-by-step math and a practical takeaway.

3. Oct 18, 2026Improvement

   Editorial review process published and homepage worked example added

   Every guide now carries an editorial byline describing how content is drafted from ASHRAE and SMACNA references and checked against the calculators. The About page documents the review process, and the Duct Sizer gained a fully worked 4,000 CFM trunk example. The unused ad placeholder box was removed.

4. Sep 26, 2026New tool

   Equivalent length, fan static, Q = V × A and unit converter

   Four new calculators. Equivalent length is derived from the same fitting coefficients as the Fitting Loss calculator (L = C × D / f).

5. Sep 26, 2026Improvement

   Printable reports and shareable links on every calculator

   Each calculator now keeps its inputs in the page address and prints a clean report with date and link.

6. Sep 26, 2026Methodology

   Calculation basis published for the Fitting Loss calculator

   Coefficient source (ASHRAE Handbook—Fundamentals 2021, Ch. 21), equations, air assumptions, units and rounding are now shown on the page. About page added.

7. Sep 24, 2026Guide

   Duct material types guide

   Roughness values, design friction-rate ranges and best uses for metal, flex and fiberglass duct.

8. Sep 23, 2026Improvement

   Shared Project Library

   Saved runs are visible to all visitors, with interpretation, next-size comparison and what changed between runs. Industry example projects added.

9. Sep 21, 2026Methodology

   Next-size comparison aligned with sizing results

   The 'calculated size' row now uses the exact displayed diameter rather than the nearest standard size.

10. Sep 19, 2026Guide

    Duct design knowledge base

    Eight guides on friction loss, friction rate, fitting coefficients, equal-friction design, critical path, static pressure and worked examples.

11. Sep 17, 2026Improvement

    Result interpretation on every calculator

    Plain-English meaning, warnings for unusual velocity or losses, what to check next, and neighboring standard sizes.

12. Sep 12, 2026Guide

    Sizing guides and velocity limits

    CFM-to-duct-size, round vs rectangular, flex vs rigid, velocity limits and standard duct dimensions.

13. Aug 30, 2026New tool

    Project plan, code compliance and contractors

    Regional cost-based project plans with PDF export, ASHRAE/NFPA/local code notes and a contractor directory.

14. Aug 13, 2026New tool

    Calculator suite

    Duct velocity, fitting loss, duct weight, rectangular-to-round converter and CFM size chart.

15. Aug 12, 2026New tool

    Commercial duct sizer launched

    Round and rectangular sizing from CFM and friction rate using Darcy–Weisbach with Altshul–Tsal friction factor.