Coast to Fat FIRE: Stop Contributing Early and Let Compounding Finish
Reference FIRE Number
$3.0M
Target Age
65
Monthly Needed
$2K
Coast Fat FIRE is the strategy of accumulating enough invested capital at a young age that compound growth alone will build a $3M portfolio by traditional retirement age — without any additional contributions. The Coast Fat FIRE number for a 35-year-old targeting $3M at 65 is: $3,000,000 / (1.07)^30 = $3,000,000 / 7.61 = $394,000. Once you have $394,000 invested at 35, you are on track for Fat FIRE by 65 without another dollar of contributions — purely through compound growth.
The Coast Fat FIRE path provides extraordinary freedom. Once you reach the coast number ($394,000–$800,000 depending on age), you only need to earn enough to cover current living expenses — no more saving required. A 35-year-old who coasts at $394,000 can reduce income to $80,000/year (enough to cover $10,000/month expenses without saving), switch to more meaningful but lower-paying work, take extended sabbaticals, or transition to part-time employment for the next 30 years while the portfolio grows to $3M.
The risk in Coast Fat FIRE is investment returns. The calculation assumes 7% real annual returns. If the market delivers 5% real instead of 7% over 30 years, $394,000 grows to only $1,700,000 at 65 — $1.3M short of the $3M Fat FIRE target. To build in a margin of safety, most Coast Fat FIRE practitioners target 110–120% of the calculated coast number: reaching $430,000–$475,000 before stopping contributions. Additionally, continuing minimal contributions ($500–$1,000/month rather than zero) provides a powerful recovery buffer if returns underperform.
The psychological appeal of Coast Fat FIRE: you reach a clear milestone (the coast number) that provides a profound mental shift. At $400,000 invested at 35, you know that — assuming reasonable market performance — Fat FIRE is secured. You no longer need the income you have. Every dollar earned becomes pure choice, not financial survival. This "financial independence psychology" even before full FIRE is one of the most undervalued benefits of the Coast strategy.