Read "How Big Is A Foot" to students. The book tells the story of a king and his quest to build a bed perfectly fit for the queen. He uses his feet to measure the correct size. But when a carpenter's apprentice builds the bed according to the size of his feet, it is not the right size. The story explains how problems with nonstandard measurements led to the use of a standard foot.
Introduce the concept of the foot. One foot is equal to 12 inches. Allow students to measure their feet to see whether they are the same size.
Explain the concept of the inch. For students who know fractions, explain that an inch is one-twelfth of a foot and that an inch is split into fractions marked by the lines between the ruler's inch marks.
Ask students to measure classroom objects, such as books, pencils, white boards and desks. Measuring in feet and inches illustrates how the two units work together.