Go to ashrae.org → search "Duct Fitting Database" → Purchase the current version (approx. $250 for non-members). That is the only reliable, accurate, and legal Excel link you will ever need. Author’s Note: Always respect intellectual property. The ASHRAE Duct Fitting Database is the result of decades of costly research. Using a legitimate copy ensures you have the correct coefficients and supports ongoing industry research.
Introduction For HVAC engineers, designers, and energy modelers, accurate pressure loss calculations for duct fittings are not just a technicality—they are the backbone of efficient system design. For decades, the ASHRAE Duct Fitting Database (DFDB) has been the gold standard reference for loss coefficients. However, the challenge has always been moving this data from static PDF tables (like ASHRAE Fundamentals Handbook, Chapter 34) into dynamic, usable engineering tools like Microsoft Excel. ashrae duct fitting database excel link
Purchase the ASHRAE Handbook on CD/DVD or Online Access (cost approx. $200–$300). The digital version often includes CSV or tabulated data for many fittings. Go to ashrae
But real fittings require two-dimensional interpolation (e.g., for W/H ratios not in the table). A basic VLOOKUP is insufficient. Author’s Note: Always respect intellectual property