This preprint presents a policy-oriented mathematical model of urban childcare accessibility, contrasting Japan’s current framework with Nordic and OECD practices. It introduces comparative indicators based on population density, transport modes, and facility quality, moving beyond fertility targets to measurable accessibility standards. The paper includes international comparison tables, optimization formulations, and appendices detailing cost ranges for facility conversion, anticipated counterarguments, and international lessons on phased regulatory relaxation. It highlights Japan’s policy gap in reflecting UNICEF and OECD recommendations and proposes actionable reforms to expand childcare facilities through conditional regulatory relaxation, targeted subsidies, and transparent KPIs. This work is intended to support researchers, policymakers, and practitioners seeking reproducible, internationally benchmarked approaches to childcare accessibility and urban planning.