But manually flipping through tables of thousands of fittings to find a "Dynamic Loss Coefficient" (C or K-factor) is a drain on productivity. Enter the solution:

=XLOOKUP([@Fitting_Ref], ASHRAE_DB[A:Fitting_Code], ASHRAE_DB[Loss_Coefficient]) If you have variable geometry (e.g., a transition where W1/W2 changes), use XLOOKUP with approximate match to find the closest geometric parameter. With coefficient C , velocity pressure Pv (in inches w.g. or Pa), the loss is:

Loss = C * Pv

In Excel: = [@Coefficient] * (0.602 * ([@Velocity_FPM]/4005)^2) for IP units. Use SUMIFS to total all losses for each air handler. This yields your fan selection point instantly. Advanced Tips: Beyond Basic Lookup Once you have the ASHRAE Duct Fitting Database Excel file, you can build advanced features: 1. Automated Interpolation Between Table Values Many fittings lack exact matches for your dimensions. Use FORECAST.LINEAR :

For HVAC engineers, mechanical contractors, and energy modelers, few tasks are as tedious yet critical as calculating pressure losses in duct systems. Every elbow, transition, tee, and damper introduces friction that your fan must overcome. For decades, the industry standard for these calculations has been ASHRAE’s Fundamentals Handbook , specifically Chapter 34 (Duct Design).

This article is a deep dive into what this database is, why it matters, how to get it, and how to leverage it to shave hours off your design time. The ASHRAE Duct Fitting Database is a digital compilation of loss coefficients for virtually every standard duct fitting used in commercial and industrial HVAC systems. Historically, these values were locked in PDFs or printed tables. Today, ASHRAE provides this data in structured formats—including Microsoft Excel.

In Duct_Calc , cell C2 (where you need the loss coefficient):