As an interdisciplinary task, factory planning represents a key factor for logistics, supply chain and ultimately, the economic success of companies in the manufacturing sector. In factory planning projects, the focus is on the early planning phase, where costs and the associated misinvestments can still be significantly influenced. The challenge lies in the early valid dimensioning of the planned factory despite fuzzy data to provide decision-making support regarding the investment costs. In this context, this article presents the development of a digital service and planning tool based on a scientific procedure model. For this purpose, the research needs are first derived, reference is made to a scientific procedure model and the requirements analysis for the tool is presented. The tool developed on this basis aims to dimension and economically assess planned factories at an early planning stage. In this way, decision-makers in companies will be provided with data-based results to make future-oriented decisions between different project scenarios.