Purpose: This is a developmental research study that aims to develop a model of polytomous scoring based-on weighting for multiple correct items in the subject of physics. Weighting was analytically applied based on question complexity and imposed penalties on wrong answers. Research Methods: Within the development model, Fenrich's development cycle, consisting of analysis, planning, design, development, implementation, evaluation, and revision, was selected throughout the cycle. The multiple correct items used have 3-4 options. The items were implemented to 140 upper secondary school students and 410 first-year undergraduate students. The students' physics ability was analyzed using the Quest program, and the results of dichotomous and polytomous scoring were compared. Findings: The results of this study showed that the analytical weighting scoring based on a complexity and penalty system on the developed assessment items generated a higher number of scoring level categories (three to seven categories) than that of dichotomous scoring (only two categories), estimated students' physics abilities more accurately and in greater detail, had an approximate distribution closer to the normal distribution, and produced a standard deviation smaller than that of dichotomous scoring. Thus, the analytical weighting scoring for multiple correct items in this study was able to produce a more accurate estimation of physics ability than those using dichotomous scoring. Implications for Research and Practice: It is recommended that the assessment of physics ability using multiple-correct items on a large scale can apply the analytical weighting scoring based on the complexity of the content and a penalty system.