The Retire Early Scenario Tool (REST) is a early retirement calculator. It helps financial planning for retirement, especially early retirement. It helps explore pathways to reach your goals, and the likelihood of running out of money. It captures key aspects including taxes, early withdrawal penalties, and health insurance that other calculators neglect and could cause you to fall short in retirement. It also captures relationships between different variables, such as how social security increases the longer your work, so you can change inputs independently and maintain meaningful results.