Background: Childhood cancer outcomes in low-middle income countries (LMICs) have not kept pace with advances in care and survival in high income countries (HICs). A contributing factor to this survival gap is unreliable access to essential cancer drugs. Lack of data on the aggregate need and cost of essential cancer drugs has hampered rational planning and acquisition in many LMICs. Methods: We created a pediatric-specific tool (FOR_xECAST) that estimates drug quantity and cost for 18 pediatric cancers, customizable to region, regimen, cancer stage distribution, and drug price. We used adapted treatment regimens developed by the International Society of Pediatric Oncology (SIOP), supplemented with input from disease experts, to model treatment approaches reflective of health-system capabilities. FOR_xECAST incorporates incidence data generated through microsimulation estimates of both diagnosed and undiagnosed (total) cases. Results: We created a pediatric-specific tool (FOR_xECAST) that estimates drug quantity and cost for 18 pediatric cancers, customizable to region, regimen, cancer stage distribution, and drug price. We used adapted treatment regimens developed by the International Society of Pediatric Oncology (SIOP), supplemented with input from disease experts, to model treatment approaches reflective of health-system capabilities. FOR_xECAST incorporates incidence data generated through microsimulation estimates of both diagnosed and undiagnosed (total) cases. Conclusions: Our results enable evidence-based forecasting of childhood cancer drug need and cost to inform health system planning in a wide range of countries. The model is adaptable to setting, diagnosis, and treatment approach, allowing decision-makers to generate results specific to their context and needs. Global estimates of essential childhood cancer drug need and cost demonstrate the comparatively small amount of aggregate resources required to treat all cases worldwide, and can help advance innovative procurement strategies with regional and international scale that drive global improvements in childhood cancer drug access.