EUCalc replies to topic a) Managing technology transition. The EUCalc project will deliver a much needed comprehensive framework for research, business, and decision making which enables an appraisal of synergies and trade-offs of feasible decarbonisation pathways on the national scale of Europe and its member countries + Switzerland. The novel and pragmatic modelling approach is rooted between pure complex energy system and emissions models and integrated impact assessment tools, introduces an intermediate level of complexity and a multi-sector approach and is developed in a co-design process with scientific and societal actors. EUCalc explores decisions made in different sectors, like power generation, transport, industry, agriculture, energy usage and lifestyles in terms of climatological, societal, and economic consequences. For politicians at European and member state level, stakeholders and innovators EUCalc will therefore provide a Transition Pathways Explorer, which can be used as a much more concrete planning tool for the needed technological and societal challenges, associated inertia and lock-in effects. EUCalc will enable to address EU sustainability challenges in a pragmatic way without compromising on scientific rigour. It is meant to become a widely used democratic tool for policy and decision making. It will close - based on sound model components - a gap between actual climate-energy-system models and an increasing demands of decision makers for information at short notice. This will be supported by involving an extended number of decision-makers from policy and business as well as other stakeholders through expert consultations and the co-design of a Transition Pathways Explorer, a My Europe 2050 education tool and a Massive Open Online Course.