Organizations need more standardization and efficiency in business process execution, which is leading them to show an increasing interest in the Business Process Management (BPM) approach. Stakeholders and workers from different departments are collaborating to obtain better products/services as a result of the BPM projects, but do not always achieve satisfactory outcomes. BPM projects must be well managed and measured for successful implementation. Software Engineering (SE) projects often use a Functional Size Measurement (FSM) technique to estimate the size of the project. This paper proposes an FSM technique for BPM, based on the Function Points metric from SE.