This paper provides an in-depth analysis of the practical applications of the definite integral. It begins by explaining the application of the definite integral to calculating the surface area of geometric figures in a plane. Examples of economic problems are also given, including output, labor productivity, and income inequality through the Gini coefficient. Based on the supply and demand functions, consumer and producer surpluses are expressed using the definite integral. Each topic is illustrated with mathematical formulas, graphs, and real-life examples, demonstrating the importance of integral calculus not only in theory but also in economic and social practice. This work is a useful resource for students of definite integrals, as well as for those who wish to apply mathematical methods to economic problems.