In this study, a sample of mathematics teachers at upper secondary level rated their knowledge with respect to the key domains described by the Technological Pedagogical Content Knowledge (TPACK) framework. The results indicated that teachers expressed that they had a high level of knowledge in terms of pedagogy and content and the combination of these, but the knowledge level was lower in terms of technology such as software installation or troubleshooting of computers. The results also indicated that there were small differences in the expressed level of knowledge between sexes and years of teaching experience. The study indicated that effective integration of digital tools should include training both in the educational use and the actual operation of the tools.