Regarding the increasing global population and the related demand for natural resources, the societal and political demand for a sustainable development has increased significantly over the last decades. Although the traditional definition of a sustainable development “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” (WCED, Our Common Future (the Brundtland Report), Oxford, 1987) appears comprehensible, it still poses a challenge to actually assess a sustainable development. As a result, sustainability assessment is becoming a rapidly developing area with a growing number of frameworks and tools with a wide range of different focus levels. Despite the variety, many of these tools are not adaptable for manufacturing companies. They are, for example, too general or focus only on specific elements. Furthermore, the existing tools usually require a lot of effort and insight data in order to be applied. Against this background, the development of a tool at the level of manufacturing companies is presented. Based on existing integrated sustainability assessment tools, a set of indicators is compiled and integrated into a framework that calculates an overall composite index combining different indicators. The developed tool distinguishes itself from other tools because it can be used from an external as well as from an internal perspective and it allows the assessment of a manufacturing company’s overall and relative sustainability with minimal time effort.