This article describes an activity appropriate for middle or high school physics or physical science students. Rather than giving the answer to the question "How does a milliliter compare to a cubic centimeter?" the students develop a procedure for measuring volume by calculation and by displacement of water. Students share the data and use graphical analysis to determine how a milliliter compares to a cubic centimeter. This procedure can be adapted to other quantities. Concepts include measurement, volume, graphical analysis of data, and measurement units.