For determining the maximum current power cables can sustain from a thermal point of view without deterioration of any of their electrical and/or mechanical properties is an important design aspect of electrical installations. The accuracy of these ampacity studies provides significant insight towards intelligently upgrading existing power cable installations and designing new ones, thus maximizing the benefits from the considerable capital investment associated with them. This article describes the salient analytical and user-interface aspects of CYMCAP for Windows, a software package dedicated to performing ampacity and temperature rise calculations for power cable installations. The package has been used around the world as a DOS application for more than a decade by power utilities, electrical consultants, cable manufacturers, and research organizations. The new version has a completely new graphical user interface, as a 32-bit application for the Windows 95 and Windows NT operating systems for personal computers. Unique features of the software include versatility in defining virtually any type of power cable and load curve, modeling of installations with more than one type of cable, modeling of multiple cables per phase, analysis of cables on riser poles, nonunity load factors, and moisture migration modeling.