A growing body of evidence including international level studies (e.g. PISA, TIMSS) demonstrate that numeracy skills (also known internationally by other terms such as mathematical literacy) is crucial for a person’s educational achievements and for informed and participatory citizenship. Early and successful interventions to improve students’ numeracy skills lie in developing and using valid and reliable diagnostic tests for numeracy skill assessment. This study explored how developing a numeracy test based on three-dimensional framework could be used for numeracy diagnostic purposes in grade 7. To achieve this, initially a three-dimensional numeracy framework based on 1) content knowledge of mathematics, 2) information literacy skills, 3) complexity levels of SOLO taxonomy, was prepared. Then the framework was used to construct a 32-item numeracy test assessing the ability to use relationships, functions and numerical information in different contexts including science. Next, the instrument was administered to 7th grade students (N = 205) in four schools who were asked to complete 3 hour-long tests. Such diagnostic data could inform teachers on students’ numeracy skills and prepare instructional materials that target specific weaknesses in class level. Further, such information could inform personalized student learning instruction and produce improved numeracy diagnostic tests for future use.