Background/Problem Statement: Measurement is the foundation for mathematical ideas without which misconceptions in counting, geometry and fraction models may arise (Wilson & Rowland, 1995). Osborne (1976) described 'measure' as an 'entity' as opposed to as a 'process.' Measuring, on the other hand, is considered as a process consisting of a comparison between an attribute of a physical object and a purposefully selected unit to quantify that attribute (Bright, 1976). One of the key measurement concepts in elementary mathematics is 'volume.' Piaget and Inhelder (1967) identified three different types of volume: occupied, interior, and complementary volume. Coordination of these volume types might play an important role in understanding the volume concept. This study focuses on developing the meaning of interior volume (capacity of a container) only.