We are making several of our engineering utilities available for free.

Enjoy, and as always, feedback is welcome.

Air Data Calculator

A free Excel add-in (“.xlam”) is now available to perform air data calculations for a standard atmosphere.


      • Airspeed
      • Atmospheric ratios
      • Compressibility corrections
      • Compressible dynamic pressure
      • Atmospheric density
      • Dynamic pressure
      • ISA deviation
      • Reynolds number
      • Speed of sound
      • Static pressure
      • Static temperature
      • Miscellaneous unit conversions for inputs/outputs.

We have found this add-in immensely useful for day-to-day calculations. It eliminates the need to look-up and re-type equations or constant values to do a quick, Excel-based calculations. The source code is VBA, installs without running a setup file, and is visible in the Visual Basic editor in Excel.

Calculations are valid for subsonic and supersonic conditions, to pressure altitudes of 65,617 feet (20 km).


Download the .xlam file to a folder on your computer, and then follow these steps within Excel.

      1. Go to Excel Options > Add-Ins to open the Add-Ins dialog
      2. In this dialog, go to Manage Excel Add-ins > click Go…
      3. Browse to your Add-in from item 2 > OK
      4. Back to Add-Ins dialog > OK
      5. Excel Add-in is already installed to Microsoft Excel with the command bar to run macros in this add-in


Functions can be accessed by typing “=Atmo“ in a cell, and then scrolling through the filtered list. Additional typing further filters the list of available functions (i.e., “=AtmoKEAS” reduces the choices to the available KEAS functions). The intuitive naming convention consists of the output parameter followed by the input arguments (in order) after the letter “f.” For instance, “AtmoKTAS_fMachOATCelsius” computes KTAS using Mach as the first input and outside air temperature (OAT) in degrees Celsius as the second input.

NOTE: by downloading or using this software you acknowledge this legal disclaimer.


Standard Atmosphere .XLAM add-in

List of functions with descriptions

As always, we welcome your comments, suggestions, and questions. Let us know how you use the add-in!



These functions are also available as a calculator on the web! Get directly to the calculation of interest for standard and non-standard atmospheres (with ISA deviation). Done in collaboration with Open Systems IO.


QNH / QFE Calculator

Coming soon - barometric pressure calculator