Coast FIRE

Coast FIRE is distinct from other FIRE variants because it is a milestone rather than an exit point from traditional employment. Once the Coast FIRE threshold is reached, the accumulated portfolio can theoretically be left untouched — no further contributions made — and compound growth at historically expected rates will carry it to a traditional full-retirement number by age 60 or 65. The individual can then shift from aggressive saving to simply covering day-to-day living expenses, freeing income that was previously directed toward retirement savings for current spending, lifestyle improvements, or lower-stress career choices.

The calculation for Coast FIRE depends on three variables: the target retirement portfolio size (often calculated as 25 times annual retirement spending using the 4% rule), the expected annual rate of return on invested assets, and the number of years until conventional retirement age. If a 35-year-old needs $1.5 million at age 65 and expects a 7% real annual return over 30 years, the present value of $1.5 million discounted at 7% over 30 years is approximately $197,000. This means a 35-year-old with approximately $197,000 invested has reached Coast FIRE — they need not contribute another dollar to their retirement accounts and can expect their portfolio to grow to the target without further savings.

The practical implication is profound: reaching Coast FIRE allows individuals to pursue less financially lucrative but more personally fulfilling careers, reduce work hours, take sabbaticals, or relocate to lower-cost areas, because the retirement savings obligation has effectively been fulfilled in advance. A person working in a demanding high-income career specifically to fund retirement savings can transition to more meaningful but lower-paying work once the Coast FIRE threshold is passed, knowing that retirement is already funded.

Coast FIRE calculations are sensitive to the assumed rate of return. Using a lower real return assumption produces a higher Coast FIRE threshold because the portfolio needs a larger starting value to reach the same terminal amount over the same period. Many practitioners use conservative real return assumptions — 5-6% rather than 7-8% — to build a margin of safety into the calculation, particularly because early FIRE timelines expose portfolios to decades of market uncertainty.

The strategy works most powerfully when started early, because compound growth over long time horizons magnifies the present-value discount dramatically. A 25-year-old reaching Coast FIRE requires a meaningfully smaller portfolio than a 40-year-old targeting the same retirement outcome, because of the additional 15 years of compounding available. This illustrates the enormous advantage of starting retirement savings early even at modest amounts, as a portfolio that reaches Coast FIRE threshold at 25 requires no further contributions over a 40-year working lifetime.

Coast FIRE is often used in conjunction with geographic arbitrage or career transitions to lower-cost lifestyles: once the retirement obligation is secured, the household can relocate to reduce current living expenses and further reduce income requirements.