The official ASHRAE Duct Fitting Database (DFDB) is not primarily distributed as a standalone Excel file, but rather as a dedicated software application that includes table data for over 200 fittings. You can access it through the following official channels: Official ASHRAE Resources
Calculate Co using VBA/Python link.
Summary of what you’ll achieve
While the official software isn't a native Excel file, most HVAC pros use the DFDB to pull accurate ashrae duct fitting database excel link
Since the database does not "live" in Excel, engineers use it to gather specific data points for their spreadsheets: The official ASHRAE Duct Fitting Database (DFDB) is