Without a conceptual understanding of fraction magnitude, students have difficulties understanding more advanced mathematics in high school and beyond. The purpose of this study is to highlight 4th and 8th grade students' misconceptions in fraction magnitude using the Trends in International Mathematics and Science Study 2015 data. The study is informed by the theory of numerical development that focuses on the understanding of the magnitude of numbers and the recognition of the location of numbers on a number line. The results indicate that fraction magnitude understanding is a challenge at the 8th grade. Implications for higher education are elaborated.