This paper proposes, in the context of low-carbon urban form, a GIS-based quantitative model to estimate carbon emission amount primarily affected by the spatial configuration of street layouts and building masses. This microscopic model is composed of the two parts: carbon emission directly caused by horizontal vehicular movements between buildings and that which is transformed from electricity consumption by vertical elevator movements within buildings. The performativity of the model is then examined through the simulation with New Town Projects in Seoul, with a special attention to their local height and grid intensification conditions. Taking carbon emission amount as a single currency, we aim through this study to idenfify the structural effects of urban form on carbon emission thus to make comparative morphological studies possible in our continuing efforts to reduce the amount of carbon emission in cities.