Federal government offices are directed by federal laws, regulations, and Executive Orders (E.O.s) to make purchasing decisions with the environment in mind. In order to help federal officials meet these requirements, the U.S. Environmental Protection Agency (EPA) created an Environmentally Preferable Purchasing (EPP) Program, which has prepared a number of resources. As they implement the green purchasing requirements, federal managers need to consider costs and advantages before making changes in their procurement and operational practices. These choices are easier if the likely benefits of proposed acquisition decisions can be demonstrated. Federal offices also face growing pressure to set strategic goals and targets and demonstrate the value of their programs in quantitative terms. For example, EPA has set a series of goals to 'green' EPA through implementation of several Executive Orders (particularly Executive Orders 13101, 13123, and 13149). This brief guide is designed to help federal offices meet these challenges. It identifies a series of existing tools and resources that can be used to help develop quantitative estimates of the projected benefits of making new EPP choices and document the estimated benefits of past EPP actions. The tools and other resources summarized here are the most useful ones we found which are currently available. They tend to focus on environmental benefits, although some address other areas such as cost savings. Some of the resources are calculators, where users can enter set inputs and obtain outputs estimating impacts in their situation. Other resources are guides, collections of policies, lists of products, data collection and tracking instruments, etc.