Units describe data. When we compare 2 kilograms to 2 square feet, the units help us to understand which is a measure of mass and which of area. In EPIC, where data are used both to calculate and present the result of carbon reduction measures, the interpretation of units is essential to the evaluation and comparison of carbon reduction strategies. EPIC uses a set of units specific to the tool's objectives. The units included in EPIC, and the consequences of their inclusion, are described below.