Determining quantitative sustainable development metrics can be difficult and requires a high effort in manual data acquisition on an institutional level, like the Word Bank or the United Nations, without adequately reflecting reality. To overcome the lack of a transparent and scalable method, which links local actions to global sustainability metrics, the Sustainability Mirror connects the Sustainable Development Goals (SDGs) with publicly and locally available data to proxy SDG metrics. By applying the approach to Germany, we calculated eight SDG metrics on a regional level. Comparing our results to two German cities, we show that the Sustainability Mirror reflects economic and ecological sustainability measures. Furthermore, we demonstrate the mirror’s scalability and spatial resolution by applying the method to each German county. Presenting a proof-of-concept, we show that proxy data can link local and global sustainability metrics. However, further research should include more social sustainability topics. Finally, we are sure our approach and its implementations can contribute to a continuous assessment of spatial and temporal spreads and changes in SDG metrics.