This knowledge note aims to summarize the relationships between urban form and greenhouse gas (GHG) emissions, for reference by practitioners and policymakers. It explores the ways in which various elements of urban form can impact the carbon of urban growth. In the context of GHG emissions, urban form is usually discussed in terms of population density, which is often visualized in terms of building heights, and its impact on transportation-related emissions. However, many different dimensions of the urban built environment, including not just density but also land use patterns, the configuration of street networks, and the materials and orientations of buildings, can impact urban GHG emissions in various ways. Urban density itself may or may not take the form of tall buildings. The impact of urban form on emissions is not restricted to its effect on transportation. The note clarifies these relationships, and also provides examples in which urban growth modeling tools quantify the emissions reductions from various growth scenarios.