<![CDATA[Abstract This research aims to determine the effectiveness of contextual learning on students' ability to understand mathematical concepts in class XI BDP1 SMK Negeri 1 Panyabungan. This can be seen from the way students answer the questions given by the teacher, where students cannot answer the questions according to the indicators of their ability to understand mathematical concepts. To overcome this problem, research suggests efforts to use contextual learning models. The population of this study was all class XI BDP with a total of 52 students. The sampling technique used was Cluster Sampling. The research sample was class XI BDP1 with ????5 students. The research method used was an experimental method with a One-group Pretest-Posttest design. And data collection techniques using observation and tests. Based on the calculation results, data was obtained that the average student score before using the contextual learning model was 6.68, when combined with the assessment criteria it fell into the "poor" category. And after applying the contextual learning model, an average score of 8.35 was obtained, when consulted with the assessment criteria it was in the "good" category. In order to know that the hypothesis that was established in this research was rejected, a differential analysis was carried out using a paired sample test, obtaining a significant value of 0.000 < 0.005, this means that the contextual learning model is effective on the ability to understand mathematical concepts of students in class XI BDP1 SMK Negeri 1 Pqnyqbungan. This means that using a contextual learning model can improve the ability to understand mathematical concepts of students in class XI at SMK Negeri 1 Panyabungan. Keywords: Contextual learning model for understanding concepts]]>
