Abstract:Reasoning based research generally examines the application of learning models or learning methods. So far, there are still rarely studies that examine the use of teaching materials to improve the quality of learning. This study aims to develop teaching materials related to the central angle and the circumference of the circle based on reasoning. The development model used is the ADDIE development model, namely Analysis, Design, Development, Implementation and Evaluation. The analysis was conducted by involving students of SMPN 1 Kabila as research subjects. The results showed the quality of teaching materials was declared valid with a percentage of 75%. Practicality of teaching materials based on the results of student questionnaire responses reached very good categories with a percentage of 82.82%. This shows that reasoning based teaching materials can be used in the learning process. Abstrak:Penelitian berbasis penalaran umumnya mengkaji tentang penerapan model atau metode pembelajaran. Sejauh ini, masih jarang penelitian yang mengkaji tentang penggunaan bahan ajar untuk meningkatkan kualitas pembelajaran. Penelitian ini bertujuan untuk mengembangkan bahan ajar materi hubungan sudut pusat dan sudut keliling lingkaran berbasis penalaran. Model pengembangan yang digunakan adalah Model pengembangan ADDIE, yaitu Analysis (Analisis), Design (Desain), Development (Pengembangan), Implementation (Implementasi) dan Evaluation (Evaluasi).  Analisis dilakukan dengan melibatkan siswa SMPN 1 Kabila sebagai subjek penelitian. Hasil penelitian menunjukan kualitas bahan ajar dinyatakan valid dengan persentase 75%. Kepraktisan bahan ajar berdasarkan hasil angket respon siswa mencapai kategori sangat baik dengan persentase 82,82%. Hal ini menunjukkan bahwa bahan ajar berbasis penalaran dapat digunakan dalam proses pembelajaran.