A guide to calculating emissions reductions from new-vehicle fuel economy and CO2 emission standards developed for Changing Transport, the transport- and climate-related activities implemented by the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ), funded by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety of Germany (BMU). Accompanying the guide is a Microsoft Excel based spreadsheet tool, FESET (Fuel Economy Standards Evaluation Tool). FESET is populated with example data from Mexico's 2012–2016 new vehicle CO2 emissions and fuel economy standards. The guide includes a step-by-step description of the Mexican example and how to apply the FESET with other country data. This guide and tool are part of the Advancing Transport Climate Strategies (TraCS) project.