The OneHealth tool is a software tool designed to inform costing, budgeting, and integrated national planning and country-level health system analysis in low and middle-income countries. The tool helps national planning teams analyze health system resource needs, cost strategic plans by year and by input, estimate health impact of interventions, and compare estimated costs with available financing. The OneHealth tool can be used by national planners to assess costing for NCD and injury programs as well as more integrated health systems based financing analyses.