While Elemental Cost Planning (ECP) is widely adopted in international construction, its integration with Building Information Modeling (BIM) remains underdeveloped in Sri Lanka. This study aims to address the absence of a standardised, automated, and NRM 01-compliant BIM-ECP solution by developing a functional Revit-based plugin capable of producing accurate, region-sensitive cost estimates. As the design methodology, this research adopts a mixed-method approach. Phase one involved developing a conceptual framework based on a literature review and validating it through surveys and expert interviews. In phase two, a plugin was developed using C# in Visual Studio, integrated with Autodesk Revit API, and tested through practical applications. The plugin automates quantity extraction, NRM-based categorisation, and cost calculations, including adjustments for time and location. The findings confirmed that Sri Lanka’s construction sector lacks tools incorporating location-specific indices and internationally accepted standards, such as NRM 01. However, private sector stakeholders expressed readiness to adopt structured tools. The developed plugin demonstrated strong potential to bridge the gap between BIM and ECP. This research presents the first BIM-integrated, Revit-based ECP tool tailored to the Sri Lankan context. It offers a replicable model for improving early-stage cost planning accuracy while supporting broader adoption of digital construction practices aligned with global standards.