Coast FIRE Calculator
Coast FIRE is the moment your invested portfolio is large enough that compound growth alone, with zero additional contributions, will fund a comfortable retirement. Enter your numbers to see your Coast FIRE target and whether you have already reached it.
What Is Coast FIRE?
Coast FIRE is the financial-independence milestone at which your invested assets are large enough that, even if you stopped contributing entirely today, compound growth alone would carry you to a fully funded traditional retirement. It is calculated by discounting your target retirement nest egg back to today's dollars using an expected real return. Once you hit your Coast FIRE number, you technically only need to earn enough to cover current living expenses — retirement is already on autopilot. This is different from Lean FIRE or Full FIRE, where you need the full nest egg now to stop working immediately.
The math: if you need $1,500,000 at age 65 to retire at a 4 percent withdrawal rate ($60,000/yr), and you are 32 with a 7 percent real return expectation, you only need roughly $154,000 invested today. Every dollar beyond $154,000 lets you "coast" — downshift, switch careers, or take entrepreneurial risk without falling behind on retirement.
Coast FIRE Formula
Coast FIRE Number = FIRE Target / (1 + real return) ^ years to retirement. The FIRE Target is your annual retirement spending divided by your safe withdrawal rate, traditionally 4 percent. Real return is the expected portfolio return minus inflation — most planners use 5 to 7 percent for a globally-diversified stock-heavy portfolio. Small changes in real return compound dramatically over decades, so being conservative (5 percent) gives a higher Coast FIRE target than being aggressive (8 percent).
This calculator uses continuous compounding and shows both your required Coast FIRE number today and your projected balance at retirement assuming zero additional contributions. If your projected balance exceeds your FIRE Target, you have reached or passed Coast FIRE.
Why Coast FIRE Matters
Coast FIRE unlocks career optionality decades earlier than full retirement. Once past it, you can take a pay cut to work on passion projects, switch to part-time, start a business, take a sabbatical year, or stay home with kids — without derailing retirement. It is a far more achievable milestone than Full FIRE for most working professionals, and it changes the psychological relationship with work from "must grind to survive" to "choosing how to spend my time."
Coast FIRE is also more resilient than Lean FIRE in downturns. Because you are still earning income, a 40 percent market crash during accumulation years does less damage than the same crash during retirement drawdown. You ride out volatility while the portfolio continues to compound.
Risks and Limitations
The Coast FIRE math assumes a steady real return, which is not how markets actually behave. Sequence-of-returns risk — a bad decade early in the coast period — can leave you short. Inflation higher than historical averages also erodes the number. The 4 percent safe withdrawal rate was modeled on 30-year horizons; if you retire early (say 55), you may need 3.25 to 3.5 percent. Always build a cushion of 20 to 30 percent above your Coast FIRE number before relying on it. Last updated: April 2026, uses Trinity Study-derived safe withdrawal assumptions.