Customizable data diagrams are provided by a data diagram software facility. The facility receives a reference to a multidimensional data set on which to base an initial data diagram. Based, at least in part, on this information, the facility generates a data diagram providing a graphical representation of nodes corresponding to data from the multidimensional data set. The facility displays the data diagram, which can be modified by a user. For example, the facility may provide tools that allow the user to change the order of the nodes of the data diagram, change the shape of the nodes of the data diagram, change the color or format of the nodes of the data diagram, etc. The facility may also provide functionality that allows the user to drill down on aspects of the data diagram based on a breakdown scheme.