There is a consensus that numeracy is important for students to develop logical thinking and reasoning strategies in their everyday activities. As a result, teachers are encouraged to design numeracy rich tasks that incorporate real-life contexts across non-mathematics curriculum areas. However, it is not clear what types of knowledge teachers require to design such tasks. In this study, the authors used the stepwise generalization method and developed a framework for the knowledge required by teachers to design numeracy rich tasks across non-mathematics curriculum areas. The study begins with a brief introduction to numeracy and its definition in various contexts. The nature of knowledge required to design numeracy rich tasks (mathematics content knowledge, a non-mathematics curriculum area knowledge, activity design skills and knowledge of context)) are further described. In the later section of the study, each element of teacher knowledge and the framework to design numeracy rich tasks across non-mathematics curriculum areas are described. The knowledge framework developed in this study can be used to analyze teachers designed numeracy-rich tasks and identify their professional learning requirements.