Environmental indexes such as carbon footprint, ecological footprint or eco-efficiency have been seriously considered in several global organizations such as the World Business Council for Sustainable Development and the World Commission on Environment and Development. In addition, environmental evaluation methods such as Life Cycle Assessment or Leadership in Energy and Environmental Design Green Building Rating System have also been considered. However, it is hard to say if the standards for evaluating the progress of a given action towards the realization of a low carbon society have been precisely established. In this paper, a standard index for evaluating actions is suggested for the realization of a low carbon society and a concrete evaluation method.