The Numeracy at Scale study was designed to identify and examine aspects of successful numeracy programs, to provide policy makers and development practitioners with evidence-based strategies for improving numeracy instruction and learning outcomes across contexts. To this end, the study team identified and analyzed six programs across five countries that had rigorous evidence of impact on numeracy learning outcomes and which were operating at scale or which showed the potential for scale in an entire region or country. In each country, the study teams carried out a mixed-methods study including quantitative observations and interviews conducted in 80 to 130 schools per country; as well as qualitative observations and interviews in ten schools per country. The Numeracy at Scale study investigated two research questions addressed in this presentation: 1) What classroom ingredients (such as teaching practices and classroom environment) lead to learning in programs that are effective at scale? 2) What methods of training and support lead to teachers adopting effective classroom practices? The programs involved in this study are based in India, Jordan, El Salvador, Madagascar and South Africa. Two of the programs are government-led. The six Numeracy at Scale programs represent a variety of designs, from providing instruction to at-risk girls via interactive software to a national-scale numeracy initiative integrated into all public primary schools. Despite their differences, these programs share a large number of common elements. This presentation will provide an overview of the common pedagogical strategies found across these successful numeracy programs, such as use of multiple representations, discussion about mathematical concepts, and targeted support for students, as well as the approaches these programs used to support the development of these practices among teachers. Drawing from qualitative data, the paper will then discuss details of how these common elements were executed differently under different program models. Both the common, key elements and “differences in the details” that are found across these programs can generate helpful guidelines and ideas for how practitioners and governments can strengthen their own numeracy professional development approaches, across different operating contexts and program designs.