Coast FIRE is a variation of the FIRE (Financial Independence, Retire Early) movement focused on reaching a savings threshold where compound growth alone will get you to your retirement target. Once you hit your coast number, you no longer need to save for retirement. You still need to earn enough to cover current living expenses, but every dollar of income can go toward present-day spending rather than future savings.

The coast number is calculated by taking your retirement target and discounting it back to today at your expected rate of return. For example, if you need $1,500,000 at age 65 and expect 7% annual returns, a 30-year-old needs about $197,000 invested today. That sum, left untouched, would grow to the target over 35 years through compounding alone.

Coast FIRE appeals to people who want to reduce financial pressure without fully retiring early. Once coasting, you might switch to a lower-paying but more fulfilling career, work part-time, or pursue passion projects, knowing your retirement is already funded by time and compound growth. The younger you are, the lower your coast number because you have more years of compounding ahead.