Greenhouse gas emissions (GHG) during the life cycle of a product, a process, or a service are the major cause of global warming and climate change. The circular economy principle has been proven to help increase resource efficiency and reduce GHG emissions. From the life cycle concept, it is known that closing loops or circularity doesn’t always generate positive environmental consequences. To ensure that circular activities are actually environmentally beneficial, the calculation of life cycle GHG emissions reduction is essential. The calculation methodology based on Intergovernmental Panel on Climate Change (IPCC) guidelines and life cycle assessment standards is described in the chapter. Case studies on opt out of plastic cutlery and upcycled fashion footwear, both from the Asia- Pacific region, are provided to illustrate the detailed calculation procedure and the GHG emissions reduction from the actual circular economy practices.