RhinoCircular is a CAD plugin developed within the Circular Construction Lab (CCL) at Cornell University that assesses a building design’s environmental impact in respect to its embodied carbon values and circularity: the degree to which design solutions minimize extraction and waste in favor of reusable, recyclable and renewable material resources. Over their full life cycle, current buildings account for 39% of carbon dioxide emissions [1] and more than 50% of resource extraction and solid waste production. [2,3] As a way to overcome the social, economic, and environmental problems of this linear economic system, the concept of the circular economy is increasingly gaining attention. Activating the built environment as a material reserve for the construction of future cities would not only provide valuable local resources, but also potentially prevent up to 50% of the industry’s emissions by capitalizing on embodied carbon. [1] However, this requires radical paradigm shifts in how we design and construct buildings (e.g. materials selection/ design for disassembly), and in how resources are managed within the built environment. Buildings and regions need to anticipate stocks and flows of materials, documenting and communicating which materials in what quantities and qualities become available for reuse or recycling where and when. RhinoCircular allows direct and immediate feedback on design decisions in respect to formal deliberations, structural considerations, material selection and detailing based on material passports and circularity indicators. It can be integrated in existing and complex workflows and is compatible with industry-standard databases while providing its own essential dataset-complementing missing information.