Penelitian ini dilatarbelakangi oleh rendahnya kemampuan pemahaman konsep matematis peserta didik di sekolah yang disebabkan kurangnya antusias peserta didik pada mata pelajaran matematika, karena metode pembelajaran yang
digunakan masih menggunakan metode ceramah, sehingga minimnya partisipasi peserta didik dalam proses pembelajaran. Selain itu belum tersedianya buku pegangan peserta didik untuk mereka belajar matematika, satu-satunya sumber pada saat kegiatan pembelajaran yaitu hanya buku pegangan guru yang mereka tulis ulang pada buku tulis masing-masing. Penelitian ini bertujuan untuk mengembangkan e-modul interaktif berbasis Project Based Learning pada materi bangun ruang sisi datar yang valid, praktis, serta dapat memfasilitasi peserta didik dalam meningkatkan kemampuan pemahaman konsep matematis. Penelitian ini menggunakan jenis penelitian dan pengembangan atau Research and Development (R&D) menggunakan model ADDIE yang terdiri dari lima tahap yaitu tahap analisis (analysis), tahap perancangan (design), tahap pengembangan (development), tahap penerapan (implemtation), dan tahap evaluasi (evaluation). Subjek penelitian ini adalah peserta didik kelas IX C SMP Negeri 2 Lebakwangi sebanyak 24 orang. Instrumen yang digunakan dalam penelitian ini yaitu lembar validasi ahli, lembar kepraktisan guru dan peserta didik, serta soal tes kemampuan pemahaman konsep matematis. E-modul divalidasi oleh lima validator ahli yaitu dua dosen pendidikan matematika, satu dosen sistem informasi, satu dosen desain
komunikasi visual, serta satu guru matematika. Hasil penelitian berdasarkan validasi ahli materi diperoleh skor persentase 92,42% dengan kategori “sangat valid”. Hasil dari ahli media diperoleh skor persentase 83,75% dengan kategori
“sangat valid”. Hasil kepraktisan guru dan peserta didik terhadap e-modul diperoleh persentase masing-masing 96,66% dan 92,36% dengan kriteria kepraktisan “sangat
baik”. Perolehan uji N-Gain berdasarkan indikator pemahaman konsep sebesar 0,70 dengan kriteria peningkatan sedang. Hasil akhir penelitian pengembangan diperoleh produk berupa e-modul interaktif berbasis Project Based Learning pada materi bangun ruang sisi datar yang valid, praktis seta dapat meningkatkan kemampuan pemahaman konsep matematis peserta didik. E-modul yang dikembangkan berbasis proyek, disarankan untuk mengalokasikan waktu sebaik-baiknya agar pelaksanaan kegiatan berbasis proyek dapat berjalan lebih maksimal dan menghasilkan output yang sesuai dengan tujuan pembelajaran.
Kata Kunci: E-modul interaktif, Project Based Learning, kemamampuan pemahaman konsep matematis.

This research is motivated by the low mathematical conceptual understanding ability of students at school, which is caused by their lack of enthusiasm for mathematics. This is due to the fact that the teaching method used still relies on
lectures, resulting in minimal student participation during the learning process. In addition, there is no student textbook available to support independent learning in mathematics. The only learning resource during class is the teacher’s guidebook, which students copy into their own notebooks. This study aims to develop an interactive e-module based on Project-Based Learning (PjBL) on the topic of three dimensional shapes with flat surfaces, which is valid, practical, and capable of facilitating students in improving their conceptual understanding of mathematics.
The research follows the Research and Development (R&D) approach using the ADDIE model, which consists of five stages: Analysis, Design, Development, Implementation, and Evaluation. The subjects of this study were 24 students from
class IX C of SMP Negeri 2 Lebakwangi. The instruments used in this research included expert validation sheets, teacher and student practicality questionnaires, and a conceptual understanding test. The e-module was validated by five experts: two mathematics education lecturers, one information systems lecturer, one visual communication design lecturer, and one mathematics teacher. The results of the study showed that the material expert validation obtained a percentage score of 92.42%, which falls under the “very valid” category. The media expert validation yielded a percentage score of 83.75%, also categorized as “very valid”. The practicality assessments by both the teacher and students resulted in percentages of 96.66% and 92.36%, respectively, which are considered “very good” in terms of
practicality. The N-Gain test result based on indicators of conceptual understanding was 0.70, indicating a moderate level of improvement. The final result of this development research is an interactive e-module based on Project-Based Learning for the topic of three-dimensional shapes with flat surfaces, which is valid, practical, and effective in enhancing students' conceptual understanding in mathematics. As the e-module is project-based, it is recommended to allocate time effectively so that project-based activities can be implemented optimally and produce outcomes aligned with the learning objectives.
Keywords: Interactive E-Module, Project-Based Learning, Mathematical Conceptual Understanding.