System dynamics is a computer-aided approach to policy analysis and design. It applies to dynamic problems arising in complex social, managerial, economic, or ecological systems â€” literally any dynamic systems characterized by interdependence, mutual interaction, information feedback, and circular causality.

The three most commonly used software packages are listed below in alphabetical order.Â Additional tools that support model construction are noted at the end.

**iThink ^{Â®}** and

**STELLA**are two names for one model development platform published by isee systems. The software is available in different configurations under a commercial license for Windows and Macintosh computers. Educational licenses and a free runtime version of the software are available.

^{Â®}**Powersim Studio** is available in a number of different configurations from Powersim Software. The software is available underÂ commercial license and runs under Windows. Educational licenses and options for publishing standalone model packages are available. A new free version, Studio Express is now available.

**Vensim ^{Â®}** is available in a number of different configurations from Ventana Systems, Inc. The software is available under a commercial license and runs on Windows and the Macintosh. Educational licenses, including a configuration of the software that is free for educational use, and a free runtime version of the software are available.

**See Also**: There are a number of other products that can be used to construct models. These include: Anylogic, Goldsim, Berkely Madonna, Sysdea and SimGua under related methodologies and MyStrategy under pedagogical tools.

Simantics System Dynamics is a ready-to-use system dynamics modelling and simulation software application for understanding different organizations, markets and other complex systems and their dynamic behavior.

ASCEND is a free open-source software program for solving small to very large mathematical models. ASCEND can solve systems of non-linear equations, linear and nonlinear optimisation problems, and dynamic systems expressed in the form of differential/algebraic equations.