If you prefer not to build from scratch, several industry sources offer Excel-based solutions:
| Template Name | Source | Key Feature | Price Range | | :--- | :--- | :--- | :--- | | HAP Duct Fitting Spreadsheet | Carrier (User forums) | Integrates with Carrier HAP load files | Free (Community) | | Elite DuctSize Excel Add-in | Elite Software | Full ASHRAE fitting database + CAD export | $199+ | | Engineering Pro Guides - Fitting DB | Engineering Pro Guides | Tutorial + pre-loaded 500+ fittings | $49 |
Note: Always verify that the Excel file cites ASHRAE Fundamentals 2021 or 2025 as the source to ensure you are using the latest (C_o) values. ashrae duct fitting database excel
For decades, calculating the pressure loss through ductwork was a tedious affair involving charts, rulers, and the iconic "Trane Ductulator" wheel. ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) formalized this data into the Duct Fitting Database.
The database contains loss coefficients ($C$-values) for hundreds of specific fittings—from round elbows to rectangular transitions, fire dampers, and junctions. The core formula it relies on is: If you prefer not to build from scratch,
$$ \Delta P = C \times P_v $$
Where $\Delta P$ is the pressure loss, $C$ is the fitting loss coefficient, and $P_v$ is the velocity pressure. The hard part isn't the math; it is finding the correct $C$-value, which changes based on geometry (e.g., the radius of an elbow or the aspect ratio of a duct). Even with a perfect Excel database, mistakes happen
Even with a perfect Excel database, mistakes happen. Watch out for these:
