Most paper-based assessment tests require students to answer all of the test items and take much time for feedbacks. Therefore, more practical, efficient, and accurate assessment model needs to be developed. This study aims to describe (1) the superiority of Computer Adaptive Test (CAT) compared to Computer Based Test (CBT) and Paper and Pencil Test (PPT) and (2) the feasibility of CAT to measure achievement in physics. The study was conducted using the following procedures: comparing Item Respond Theory (IRT) with Classical Test Theory (CTT), comparing CAT with CBT and PPT, and conducting surveys to assess CAT performance to measure physics achievement. The result shows that, in case of education in the 21 st century, (1) CAT is more superior to assess students' achievement in physics than CBT and PPT; and (2) CAT is more feasible to measure physics achievement. Therefore, CAT is very appropriate to assess physics learning nowadays.