Ashrae Duct Fitting Database Excel Jun 2026

Accurate pressure drop calculation is the foundation of efficient HVAC design. Oversized ducts waste material and space, while undersized ducts lead to noisy systems and overworked fans. For decades, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has provided the gold standard for these calculations through the ASHRAE Duct Fitting Database (DFDB).

Many ASHRAE fittings require interpolation because actual design dimensions fall between the discrete values listed in the database tables. If a rectangular elbow has an aspect ratio (

The ASHRAE Duct Fitting Database (DFDB) is a professional software tool used to calculate pressure losses in HVAC duct systems . While ASHRAE does not provide a standalone Excel file,

-factor varies dynamically based on geometric ratios (e.g., aspect ratio, radius ratio) and flow ratios (e.g., flow rate fractions in branches vs. mains). ashrae duct fitting database excel

When working with ASHRAE data in Excel, be mindful of the following considerations.

[System ID] -> [Segment Description] -> [Airflow (CFM)] -> [Duct Size] -> [Velocity (FPM)] -> [Velocity Pressure (in. w.g.)] -> [Fitting Code] -> [Looked-up Co] -> [Fitting Pressure Drop] -> [Cumulative Loss] 3. The Summary Dashboard

Which (e.g., supply elbows, tees, or entries) do you use most often? Accurate pressure drop calculation is the foundation of

A free mobile app for iOS that includes a subset of common fittings for quick field use.

: It covers round, rectangular, and flat oval duct fittings for supply, exhaust, and common duct functions. Integration with Excel

The database, which draws its data directly from the ASHRAE Handbook—Fundamentals, includes loss coefficient tables for more than 200 round, rectangular, and flat oval duct fittings. It covers fittings for supply, exhaust, and common (supply/return) duct functions, allowing you to enter fitting-specific information—such as geometry, category, and dimensions—to obtain precise data. mains)

The article presents a complete Excel spreadsheet that can be downloaded from ASHRAE’s website, containing UDFs for duct diameter, flow, pressure drop, and rectangular equivalents. The procedure described follows a five‑step iterative method:

Do you design in (CFM, inches w.g.) or SI units (L/s, Pascals)?

The challenge is that each fitting has a different set of geometric parameters. For example:

On your main calculation sheet, create a row-by-row layout representing the duct run from the fan to the terminal device. Your columns should include: (e.g., Fan Discharge to Elbow 1) Airflow (CFM): Volume of air flowing through the section.