Do humanitarian workers really trust numbers? In the realm of the DATAWAR research project, this article aims to investigate the interest that humanitarian workers have developed towards quantitative data in the last two decades. The ‘needology’ approach (Glasman, 2020), growing expectations of donors since the 2000s, and the professionalisation and rationalisation of the humanitarian field are all factors that have contributed to the massive use of quantitative data. Discourses promoting ‘evidence-based humanitarianism’ have fostered massive hope in the humanitarian community: a good use of quantitative data could enhance contextual analyses, intervention monitoring or even the safety and security of humanitarian workers. However, this study has discovered that these narratives overestimate the ease with which humanitarian workers deal with numbers. In fact, it shows that the use of quantitative data is mainly determined by a specific, restrictive, hierarchically oriented evidence-based system which nurtures bottom-up accountability rather than day-to-day project management. As a result, the datafication of the humanitarian field does not seem to have been accompanied by an improvement of the data literacy of humanitarian workers.