The aim of this thesis was to examine which view students in four different grade three have on the equality sign. There are two main classifications how students understand the equal sign; operational as a sign that wants you to do something so there will be a result and relational as a sign that shows an equal relation between both of it’s sides. This is the mathematical theory my study is based on. For a more holistic view on learning I used the sociocultural perspectiv as a superordinate theory. The main method I used in this study was a math test that I constructed after reading international studies on this topic and doing a pilot test. The other method was a structured interview with the math teachers for getting an overview about how they taught the equality sign and their thoughts about it. The design of my study had the goal to investigate how do students in grade three understand the equality sign. Most of the students could solve relational math tasks even though only half of them explained the meaning of the equality sign relational. Students who had math difficulties solved only less than half of the relational math tasks and only one of them defined the equality sign relational. Students who defiened the equality sign as relational could solve more relational math task than the group who defined it operational although even they could solve a majority of the relational math tasks.