Here we introduce the Monash Electrochemistry Simulator (MECSim) software package that allows most aspects of ac voltammetry to be simulated when a single sine wave or a combination of sine waves are superimposed onto a dc ramp. The MECSim software and companion tool kits can be downloaded free of charge from http://www.garethkennedy.net/MECSim.html where there is also instructional documentation. Features accommodated in the simulation model include non-linear background capacitance, uncompensated resistance, Butler–Volmer and Marcus–Hush electron transfer, chemical reactions involving surface confined and solution phase species and stationary or rotating disc electrode mass transport with linear diffusion. Companion tool kits are also provided that allow Fourier transformed ac voltammograms with harmonic analysis to be generated along with other forms of data presentation. The MECSim format in combination with parameter optimisation tool kit also facilitates the implementation of sophisticated forms of experiment-theory comparisons needed to estimate the electrode kinetic and other parameters. MECSim software is computationally efficient and based on flexible code that can be used in cluster computing as well as on a single machine. Typical simulations take seconds to run on a laptop and parameter searches needed to tackle the inverse problem can be achieved efficiently. Capabilities of MECSim are illustrated in this article by comparing simulated results with those obtained experimentally.