Simfit is a free open-source Windows package for simulation, curve fitting, statistics, and plotting, using a library of models or user-defined mathematical equations. Simfit has been developed by Bill Bardsley of the University of Manchester.^[1] Although it is written for Windows, it can easily be installed and used on Linux machines via WINE.^[2]

Simfit is developed using Silverfrost Limited's FTN95 Fortran Compiler and is currently featured on their website as a showcased application. The graphical functionality in Simfit has been released as a Fortran library called Simdem which allows the programmer to produce charts and graphs with just a few lines of Fortran. A version of Simdem is shipped with the Windows version of the NAG Fortran Builder.^[3]

A Spanish-language version of Simfit is maintained by a team in Salamanca.