The methodology for atomic scale calculations of electrocatalysis in order to identify mechanisms and estimate reaction rates is reviewed. These include: (1) the application of an external electrical field or potential in density functional theory calculations, (2) the thermochemical model for estimating the onset potential of an electrochemical reaction, and (3) calculations of transition paths in atomic scale models of the electrical double layer. Hydrogen evolution reaction, oxygen reduction reaction as well as CO2 and N-2 electrochemical reduction to form methane and ammonia are taken as examples. Calculations of reaction rates based on the estimation of the activation energy of elementary steps from minimum energy paths and transition state theory have been shown to provide accurate estimates of rates even for complex reactions and competing reaction mechanisms. There is room, however, for further improvements and some of those are also mentioned at the end of this mini-review.