Gross Domestic Product (GDP) has long been considered the primary indicator of economic performance and development. However, excessive reliance on GDP alone often overlooks critical dimensions of human well-being, environmental sustainability and social equity. In the contemporary era marked by climate change, inequality and resource constraints the concept of development has expanded beyond mere economic growth to include sustainability and social welfare. This research paper critically examines the concepts of GDP, GNP, NNP and Per Capita Income (PCI), evaluates their relevance and limitations and integrates them with the broader framework of sustainable development and social sustainability. Using secondary data sources, the study presents year-wise Indian GDP trends, compares traditional growth indicators with sustainability oriented measures and maps economic development goals with the United Nations Sustainable Development Goals (SDGs). The paper argues that while GDP remains an important economic indicator, it must be complemented by sustainability metrics to achieve inclusive and long-term development.