Improving nitrogen use efficiency in rice is important for better crop production and environmental protection. In this study, different conventional indica rice cultivars were grown to see how they use nitrogen for grain output. The cultivars were grouped into 6 types based on their nitrogen use efficiency levels. The ones with higher nitrogen use efficiency had higher yields and better grain production. They also had more panicles, better grain setting, and higher harvest index. By improving nitrogen uptake and efficiency, rice cultivars can achieve higher yields. The study showed that there are significant differences in nitrogen use efficiency among rice cultivars, and those with higher efficiency have better overall performance in terms of yield and grain production.