Feature-oriented programming (FOP) is a programming technique to implement software product lines based on composition mechanisms called refinements. A software product line is a set of software systems that share a common, managed set of features satisfying the specific needs of a particular market segment. The literature reports various software metrics for software product lines developed using object-oriented and aspect-oriented programming. However, after a literature review, we observed that we lack the definition of FOP-specific metrics. Based on this observation, this paper proposes a set of eight novel metrics for feature-oriented programming. These metrics were derived both from our experience in FOP and from existing software metrics. We demonstrate the applicability of the proposed metrics by applying them to a software product line.