The aim of this study was to examine the views of key experts on developing and using cost-effectiveness calculators to plan and evaluate health and wellbeing promotion interventions in health and social services. Data for this qualitative interview study were collected from 14 Finnish experts in health and wellbeing coordina-tion, health and social service management and research and health economics in spring 2021. A semi-structured interview method with thematic analysis was used. The experts said that there is a need for cost-effectiveness evaluation tools that support local evidence-based decision-making. This would enable organiza-tions to plan and allocate scarce resources for interventions that promote equitable and effective health and wellbeing. However, practical tools and calculators that enable users to make decisions based on the best available evidence are not widely used. Local decision-makers, researchers and service providers all need to be involved in agreeing goals and selecting the right target groups and measures. They also need to make decisions about the best available data sources and how to use calculators to define and evaluate outcomes. Cost-effectiveness calculators are needed for local evidence-based decision-making, so that municipalities can allocate scarce resources to effective services that increase the wellbeing and equality of residents. This requires key stakeholders to work together to plan, develop and evaluate comprehensive, easy-to-use cost-effectiveness calculators.