Social programs are crucial to reduce poverty and inequity in developing countries. The operation of social programs, however, cannot be improved with traditional engineering tools since these tools are designed to maximize profits: in social programs maximizing profits is not the objective, social sustainability is. Field research was conducted and it was found that the operation of social programs is considered more socially sustainable if it meets two criteria: Efficiency and Equity; in other words, if the program can help more people who need it the most. This paper proposes a methodology centered in the development of mathematical formulas for the concepts of Efficiency and Equity, so that, by being able to measure them, government programs operation can be enhanced with engineering tools. The methodology is illustrated with a case study, a subsidized milk distribution program in Mexico, called Liconsa. Once the formulas were developed and used in a simulation model for Liconsa, different policies were tested and their results regarding Efficiency and Equity were compared. Results showed the best policies for Liconsa are the balanced ones: where help is increased for beneficiaries, while cost reduction commitments are obtained. In the discussion it is argued how the developed Equity and Efficiency indicators help to understand the tradeoffs between the objectives in opposition: instead of analyzing dozens of indicators, some of them improving and others worsening, the two formulas allow to capture all effects into two objectives and evaluate decisions based on their integral impact. Conclusions show that the mathematical definition of Equity and Efficiency supports better and more informed decision making towards improving the social sustainability of the programs operation. The mathematical definition of Equity and Efficiency and its use in engineering models helps balance the opposing objectives of social programs operation and promotes better and faster changes towards more socially sustainable programs.