What is Coast FIRE? Coast FIRE is the point where your existing investments, left untouched, will grow to a full FIRE number by traditional retirement age, meaning you no longer need to contribute new savings and can “coast” by earning just enough to cover current expenses. It is the earliest milestone on the FIRE ladder and the one most achievable for workers in their 20s and 30s.
The formula: Coast Number = FI Number ÷ (1 + r)^n, where r is your expected real return and n is years to retirement. Example: a 30-year-old targeting $1,000,000 by age 65 with a 7% real return needs just $93,663 invested today. Every dollar after that compounds on autopilot. Compare to the full FIRE number, which requires roughly 10x more capital.
Coast FIRE unlocks massive lifestyle flexibility: you can downshift to a lower-paying but meaningful job, take a mini-retirement, or go part-time, because you only need to cover living expenses, not savings contributions. It is the secret weapon of parents, creatives, and career-switchers who refuse to grind until 40.