Untilfree is a FIRE calculator for iPhone. Enter four numbers (age, savings, monthly investing, monthly spending) and get one date when work could become optional, shown as a cautious, likely and optimistic range. Switch between the 4% rule and dividend income, price a purchase in days of freedom, and try "what if" changes. No account, no bank link. Free with ads; Plus removes ads and adds extras. A planning tool, not financial advice.