NewByte has been developing flight simulation tools for the PC platform since '88. Here is a free tool to calculate standard atmospheric conditions (ISA) at a given geometric or pressure altitude and ambient temperature. At those conditions, it is possible to convert between Mach number, Calibrated air speed (CAS) and True air speed (TAS). Geometric altitude is the true altitude above sea level while pressure altitude is the expected reading on an aircraft altimeter set to standard QNH.
As this calculator has became very popular, especially with airline pilots and industry engineers, we have decided to develop a stand alone freeware app that will give more functionality and user friendliness. If you have any comments please send us and we'll try to implement them at the next software release.