The Handbook is a comprehensive, step-by-step guide to costing gender equality priorities. It responds to the growing demand for guidance on estimating the financing gaps and requirements for achieving gender equality commitments and builds on UN Women's decade long work on gender responsive planning and budgeting. The Handbook is organized into three sections: Section I explores the rationale for costing gender equality and introduces the main approaches and methods; Section II outlines the step-by-step process for undertaking a costing exercise; and Section III presents five case studies featuring costing work on gender equality. The handbook is designed to support UN Women country offices, governments, multilateral and bilateral organizations and civil society in costing gender equality outcomes.