Coast FIRE Baseline 2027 Calculator

Coast FIRE vs Traditional FIRE

Traditional FIRE = save aggressively, retire at 35-45, live off portfolio forever. Coast FIRE = save enough early that compound growth alone reaches FI by traditional retirement (65), even with zero further contributions. The savings phase ends at 35-45 but actual retirement waits until 65. Practical advantage: once Coast FIRE is hit, you can drop to a job you actually enjoy, or work part-time, without sabotaging long-term security.

The Math of Coasting

Coast FIRE Number = FI Target / (1 + expected return)^years to retirement. At 6% real return, 30 years to retirement, your Coast number is 17.4% of the FI number. A $2M FI target requires only $348k at age 35 to coast to $2M by 65. The remaining 30 years require zero new savings — pure compounding handles the rest. At lower expected returns (4%), the Coast number rises to 31% of FI ($617k).

Why It Beats Traditional Saving

Hitting Coast at 35-45 lets you stop saving 20-30% of income for retirement. That saved cash flow ($15-30k/year) can buy: a smaller mortgage paid off faster, family time during peak parenting years, a sabbatical, career pivots, or simply better quality of life. The trade-off is later retirement (65 vs 45-55) but with substantially better intermediate years.

Risks of Coast FIRE

Real return assumption is the biggest risk. If you assume 6% but realize 3%, your Coast number was understated by 30-40% — leaving you short at 65. Solution: assume conservative 4-5% real return when computing Coast. Also: sequence-of-returns risk in the last decade — a major bear market at age 60-65 with no contributions to dollar-cost-average through can hurt. Some Coast FIRE practitioners continue minimal $5k-10k annual contributions to hedge.

Sources: mrmoneymustache.com FIRE math, bigerncents.com Coast FIRE guide, fed Trinity Study 4% rule. Last updated: May 2026.