Two theories are available to predict the values of the rate constants of electron transfer between a redox species and an electrode as a function of electrode potential: the Butler-Volmer theory, and the Marcus "Density of States" (MDoS) theory. While the Butler-Volmer is purely empirical, it is widely used, in part because of its ability to represent experimental data, but also because of its simplicity: the rates are just exponential functions of the potential. By contrast, in the case of the MDoS theory, whose justification comes from the well-established theory of electron transfer proposed by Marcus, the rates are expressed in the form of indefinite integrals, which are harder to compute. A number of algorithms have been presented in the literature, with various merits in terms of accuracy and computation time; however, these algorithms have never been compared under the same conditions, which prevent making informed choices. We systematically compared the algorithms, both in terms of accuracy and computation time, and also propose a new algorithm which is very fast and reasonably accurate.