Mathematical equivalence is crucial throughout the entire course of education. Understanding the concept is a prerequisite for comprehending mathematics, especially in algebra. Despite this, research indicates that many students lack a relational understanding of the concept, both early in their educational journey and as they progress through the grades. However, certain studies suggest that students can demonstrate relational understanding, even at younger ages, as long as you don’t use linguistic assessment methods. This study focuses on primary school students and their understanding of mathematical equivalence. The aim of the study is to investigate whether third-grade students possess a relational understanding of equivalence and, if so, to explore its characteristics. To examine this, a survey was used with math tasks to assess students at a school in southern Sweden’s understanding of equivalence. The surveys have been analyzed through radical constructivism and the Mathematical Equivalence Assesment model. The results indicate that a significant portion of students exhibit partial or complete relational understanding of equality. Furthermore, the findings reveal that students lacking an understanding of the definition of mathematical equivalence attain considerably lower results compared to those with such an understanding. An overarching conclusion that can be drawn in relation to the study's results is that a relational understanding of mathematical equivalence is crucial for long-term learning in mathematics.