The Centre For Design at RMIT University describes ecological footprints as "a tool for measuring and communicating the environmental impacts of human activity on the environment, and the sustainability of that activity. They are based around the concept that human consumption of goods and services require a large range of inputs from the environment, and that the environment has limited capacity to supply these inputs. Ecological footprints measures these inputs in terms of land required to sustainably produce these inputs and compare this to the land available within a region or across the world."
EPA Eco-Footprint Calculator
EPA Eco-Footprint Calculator