Coasting refers to the period where you no longer need to add more money to your retirement accounts. You have built a critical mass of capital that, thanks to the exponential power of compound interest, will grow to your goal by the time you reach retirement age. This allows you to potentially switch to a lower-stress job, work part-time, or simply enjoy 100% of your current income without the guilt of not saving for the future.

The calculator works in reverse. First, we determine your "Full FIRE" goal based on your expected retirement spending (usually your annual expenses multiplied by 25). Then, we adjust that goal for future inflation. Finally, we move that future value back to the present day using the expected rate of return on your investments. If your current portfolio exceeds this value, you are Coast FIRE.

Coast FIRE is a game of time. The younger you are when you achieve this milestone, the more powerful the results. This is because every dollar has more decades to double and triple. For someone in their 20s, a Coast FIRE number might be surprisingly small—sometimes under $100,000—because it has 40+ years to grow into millions. This highlights the vital importance of "Front-Loading" your investments early in life.

Inflation is the "silent killer" of retirement plans. $40,000 today will feel like a much smaller amount in 30 years. Our calculator builds inflation directly into the target number. When you see your Coast FIRE amount, it represents exactly what you need today to match that *purchasing power* in the future. We generally recommend using a 7% nominal return and 2% inflation for a conservative and realistic 5% "real" growth rate.

Reaching Coast FIRE gives you options. You can continue saving as before to reach "Full FIRE" even earlier. However, many people take this opportunity to redesign their lives. You could take a "mini-retirement," start a business you're passionate about, or focus on work that pays less but provides more joy. You have mathematically won the retirement game; now you're just playing for side quests.

The primary risk is a prolonged period of poor market returns (the "lost decades"). Because Coast FIRE relies heavily on growth rather than additional contributions, your success depends on the market's long-term performance. It is always wise to revisit your calculations annually and perhaps maintain a "safety margin" by continuing to contribute small amounts if you enjoy your work.