The database is organized by fitting shape (Round, Rectangular, Flat-Oval) and by fitting type. Here are the major categories within the 2016 release:
While the 2016 version was a desktop staple, ASHRAE has since transitioned the tool to a model. For field use, the ASHRAE DFDB Lite app (available on the Apple App Store) provides a subset of these fittings for quick calculations on iPhone and iPad. Duct Fitting Database - ASHRAE
The 2016 database allows engineers to see the drastic difference in $C$ values between a mitered elbow without vanes ($C \approx 1.3$) and a smooth radius elbow with a long radius ($C \approx 0.15$). This data drives design decisions that save energy. ashrae duct fitting database 2016
To understand the utility of the database, one must look at the categories it covers. The organizes components into specific groups, identified by a coding system (e.g., ER for Elbow Rectangular, TR for Transition Rectangular).
The is more than an archive—it is a practical tool that continues to drive accurate, efficient duct design. Whether you are calculating pressure drop for a 10-inch round elbow or a complex rectangular tee, the 2016 edition offers validated, well-documented coefficients. The database is organized by fitting shape (Round,
The 2016 database separates these clearly. Do not use a rectangular elbow coefficient for a flat-oval elbow with equivalent diameter—the vortex shedding characteristics are different.
Do not rely on "free" PDFs found on random engineering forums. The 2016 database has been widely pirated, but many of those copies contain OCR errors (e.g., a C factor of 0.24 becomes 0.84). Always verify with a legitimate source. Duct Fitting Database - ASHRAE The 2016 database
However, for retrofits, existing building models, and projects designed between 2016 and 2024, the 2016 database is the correct reference. Using a newer database to analyze an older system can create an "apples-to-oranges" comparison, because fitting loss coefficients sometimes change between editions due to updated test methods.