for quick field calculations, which includes a subset of common fittings and allows results to be emailed as spreadsheet attachments for further analysis. How to Build Your Own Excel ESP Calculator

A modern alternative to VLOOKUP that allows for exact or next-smaller/larger element matching, which is ideal for interpolating between listed duct sizes.

Smooth radius elbows are characterized by the r/D ratio (radius of curvature divided by diameter). A 90° smooth radius elbow with R/D = 1.5 serves as a common baseline in examples; its loss coefficient depends on the Reynolds number and can be found in the database.

) represents the aerodynamic resistance of a specific fitting geometry. It dictates how much total pressure is lost as air flows through a bend, transition, or junction. The Core Pressure Drop Equation To find the actual pressure drop (

=IF(Velocity_FPM * Hydraulic_Diameter_Ft / Kinematic_Viscosity < 4000, Use_Transition_Coeff, Turbulent_Coeff)

It covers both rectangular and round ductwork, including various fitting geometries.

Here’s a practical feature set for an , organized by utility:

This legacy version includes loss coefficient tables for more than 200 fittings and features an important capability: users can export fitting table coefficient data to the Windows clipboard. These data can be easily pasted into most Windows programs, including Microsoft Excel. Version 5.00.00 purchasers receive instructions on how to download the latest update (5.00.10) free of charge.

When we refer to the , we are talking about a spreadsheet (or a set of CSV/Excel files) that contains:

The ASHRAE Duct Fitting Database (often referred to as DFDB) is a comprehensive collection of pressure loss coefficients (

ΔP=C0×Pvcap delta cap P equals cap C sub 0 cross cap P sub v ΔPcap delta cap P