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Evaluating developer contributions is essential for effective resource allocation and recognizing expertise. Traditional metrics—such as lines of code (LOC) or commit counts—lack sufficient context, as code varies in complexity and importance. Reusable code, however, is a key indicator of quality and can serve as a better metric for contribution evaluation. Our goal is to develop a methodology and practical tool to assess developers’ reusable code contributions in software projects. Inspired by Hirsch’s H-Index used in academia, we introduce the Developer H-Index (DH-Index), which tracks method usage through project-wide call graphs, analogous to academic citations. These usage references are linked to individual developer contributions. We further propose the Lines-of-Code- Weighted Developer H-Index (LWDH-Index), which incorporates method length to account for the significance of reused code. We implemented this approach in DevScholar, an open-source prototype that analyzes Java project repositories to extract method-based developer metrics. We evaluated DevScholar against GitHub Insights using two Open-Source Software (OSS) projects: Spring Boot and Apollo. The LWDH-Index proved more robust, reducing the distortion caused by overly simple but frequently reused methods or complex methods used sparingly. Additionally, we conducted a user study with an international airline company, analyzing three internal projects. Our findings suggest that, compared to traditional LOC- or commit-based metrics, DH-Index and LWDH-Index offer richer insight into the impact and quality of developer contributions, particularly in terms of code reusability. This contributes to a more nuanced understanding of developer performance in team-based software development.