Measurement concepts such as volume and surface area provide rich contexts for real-world applications of number processes. Despite their importance, many students and prospective teachers show superficial understanding of measurement concepts. A lack of spatial reasoning and integration of geometric knowledge in problem solving situations may be the cause. This study seeks to determine the connection between spatial reasoning and discourse in influencing students' mathematical reasoning in measurement situations. We analysed 118 year 8 to 10 students' responses on two scenarios: (1) manipulation of 3D relations in 2D format and (2) explanation of changes in the volume and surface area of a shoe box after enlargement. The results showed that successful reasoners demonstrated a connected, integrated abstraction between numerical and geometric schemes, leading to success in reasoning about volume and surface area situations.