Metric scale is an important concept taught as part of science curricula across different countries. This study explored metric and relative (body-length) scale concepts of inservice ("N"?=?92) and preservice ("N"?=?134) teachers from Austria, and Taiwan, and their concepts were compared with those of teachers from the USA. Participants completed three assessments: the "Scale Anchoring Objects" (SAO), "Scale of Objects Questionnaire" (SOQ), and a subsample of participants were interviewed with the "Learning Scale Interview." A Rasch analysis was conducted with the SAO and SOQ and results showed that the Rasch model held for these assessments, indicating that there is an underlying common dimension to understanding scale. Further analyses showed that accuracy of knowledge of scale measured by the SAO and SOQ was not related to professional experience. There were significant differences in teachers' accuracy of scale concepts by nationality. This was true for both metric and body-length SAO assessments. "Post hoc" comparisons showed that the Austrian and Taiwanese participants were significantly more accurate than the US sample on the SAO and SOQ. The Austrian participants scored significantly higher than the US and the Taiwanese participants. The results of the interviews showed that the Taiwanese experienced teacher participants were more likely to report learning size and scale through in-school experiences than the Austrian or the US participants. US teachers reported learning size and scale most often through participating in hobbies and sports, Taiwanese teachers reported learning scale through sports and reading, and Austrian teachers most often noted that they learned about scale through travel.