It is not easy to assess the matching of supply and needs in terms of early childhood services in a large city. Given the diversity of childcare arrangements and the prominent place held by collective structures, a wide variety of parameters have to be factored in to evaluate the potential supply available in this area. On the other hand, assessing current needs requires identifying social-economic profiles of families, their requests, and combining these two types of data. This assessment was performed in Nantes. A cross-analysis of supply and needs revealed that the city had the theoretic capacity to meet its population’s demands in terms of regular child care services, but that tensions appeared during certain periods of the year, in specific territories and/or with specific groups. In spite of its limits, this evaluation offers a framework where all local actors can contribute data on family behaviours, childcare operational modes and ongoing evolutions in this domain. It allows them to share information on local realities and to respond better to current needs in their territory.