This study was a small scale cross-country comparison of elementary school teachers’
pedagogical content knowledge for teaching length estimation. A total of 35 in-service
elementary school teachers (22 Taiwanese and 13 German teachers) participated in
one-on-one semi-structured interviews. Results showed that the majority of teachers in both groups appreciated the value of the guess-and-check procedures for teaching
length estimation. There were differences in the two groups’ knowledge of the use of
estimation strategies for teaching students to make estimations. No differences existed in the two groups’ knowledge of students’ estimation skills. Suggestions for improving teacher’s knowledge for teaching length estimation are suggested