Evaluating the costs and impact of transformative agreements: introducing the DEAL Cost Modeling Tool In order to budget for open access publishing-based costs (as opposed to subscription-based costs) and, more generally, project and evaluate the financial impact of Germany’s nationwide DEAL transformative agreements, libraries in Germany need to have a complete overview of their publishing profile and the related cost trends—something not fully tracked as yet in most libraries. To help libraries easily gain such insight, MPDL Services GmbH presents the DEAL Cost Modeling tool: https://deal-operations.de/en/here-is-the-deal/deal-cost-modeling-tool And, for both German librarians and the broader community, the Tool is complemented by a discussion paper which provides a summary of key findings, approaches and visualizations gleaned from the Tool. Direct access to the discussion paper is available here: http://hdl.handle.net/21.11116/0000-0008-EEBC-9 The DEAL Cost Modeling Tool is an interactive, Excel-based tool that incorporates industry-standard bibliographic and financial data with a robust methodology to give every library comprised in the nationwide DEAL agreements the ability to calculate their total costs with the publishers Wiley and Springer Nature, automatically. With the Tool’s input and setting options, users can generate custom projections to assess long-term savings, or funding requirements needed, and compare their projected costs under the conditions secured with the DEAL agreements, with potential costs under the previous subscription-based system and other scenarios. The Tool comprises editions specific for each publisher, a discussion paper, and a user guide. All materials are available in German and English. Best wishes, Colleen Campbell Open Access 2020 Initiative ESAC Initiative Max Planck Digital Library campbell@mpdl.mpg.de +49 160 9725 1536 ---------- Dr. J. K. VIJAYAKUMAR, King Abdullah University of Science & Technology (KAUST), www.kaust.edu.sa