Effort estimation is still one of the most daunting, hard to apply tasks in any given software project. Although many current methodologies propose an incremental approach to software development, there are still few techniques that allow them to be applied efficiently. We developed TUPUX, an add-in component for StarUML that facilitates the planning and estimation, using Function Points, in software projects that adopt the incremental model. The technique supported by our tool has been tested in several undergraduate-level software development projects, yielding promising results. Additionally, our software supports use-case specification as a previous activity to effort estimation. It also employs analysis class diagrams to facilitate a semi-automated Function Point counting process to be applied. © 2009 IEEE.