What Is Coast FI?
Coast FI (Coast Financial Independence) is a milestone that answers one specific and liberating question: how much do you need invested right now so that, even if you never contribute another dollar, compound growth alone will grow that balance to your full retirement number by a target age?
Once you reach your Coast FI number, you are no longer racing to save for retirement. You only need to earn enough to cover your current living expenses. You can "coast" to retirement on the growth already in motion.
The concept is part of the broader FIRE (Financial Independence, Retire Early) movement but appeals to a much wider audience than traditional FIRE because it does not require an extreme savings rate indefinitely. It requires an intense savings period early on, followed by a much more relaxed financial existence for the remainder of your career.
The Math Behind Coast FI
The calculation is straightforward present value math:
Coast FI Number = Target Retirement Portfolio / (1 + annual return rate)^years until retirement
Your target retirement portfolio is your full FIRE number, typically 25x your annual expenses using the 4% rule. The formula discounts that future number back to today using your expected investment return. The result is how much you need invested now for compound growth to close the remaining gap without further contributions.
Example: You need $1,500,000 to retire. You plan to retire at 65 and you are 30 now, giving you 35 years. At 7% expected annual return:
Coast FI Number = $1,500,000 / (1.07)^35 = $1,500,000 / 10.68 = $140,450
If you have $140,450 invested at age 30 and never contribute another dollar, compound growth alone will deliver approximately $1,500,000 by age 65. Your retirement is already funded in principle. The only thing left to do is not withdraw the money and not stop it from compounding.
That $140,450 threshold is dramatically lower than the $1,500,000 goal. This is the power of time and compounding. A dollar invested at 30 is worth 10.68 dollars at 65 at 7% growth. A dollar invested at 50 is worth only 3.87 dollars at 65.
Why Coast FI Matters Even If You Never Plan to Retire Early
Coast FI is not just a tool for people targeting early retirement. It is valuable for anyone who wants to understand how much financial pressure they have already removed from their future.
Reduced financial anxiety. Knowing that your retirement is already mathematically secured changes how you approach work, spending, and career decisions. You can take a lower-paying job you enjoy more, take a sabbatical, or reduce your hours without feeling like you are derailing your financial future.
Career flexibility. If you reach Coast FI at 38, you no longer need a high income to maintain a secure retirement. You need to cover your living expenses, which opens up a much wider range of employment options.
Downshifting. Many people in the FIRE community use Coast FI as a stepping stone to "Barista FI" or "Semi-Retirement," working part-time or in lower-stress roles that cover expenses without the pressure of aggressive saving.
A concrete early milestone. Full FI can feel impossibly distant for many savers, especially early in their careers. Coast FI is a reachable target on the way there that has real, tangible meaning.
Coast FI by Age: Reference Points
Assuming a $1,000,000 target retirement portfolio and 7% annual return, here are the Coast FI numbers at different current ages:
| Current Age | Years to 65 | Coast FI Number (for $1M target) |
|---|---|---|
| 22 | 43 years | $58,200 |
| 25 | 40 years | $72,000 |
| 30 | 35 years | $94,000 |
| 35 | 30 years | $131,400 |
| 40 | 25 years | $184,200 |
| 45 | 20 years | $258,400 |
| 50 | 15 years | $362,400 |
| 55 | 10 years | $508,300 |
The dramatic decline in Coast FI numbers as you look at younger ages illustrates why time is the most powerful variable in investing. A 22-year-old who saves $58,200 by their mid-20s has effectively funded their entire retirement, even if they never invest another dollar. Achieving that in the first few years of a career is realistic with a high savings rate and no student loans, or achievable by the late 20s even with modest student debt.
For a $2,000,000 target, simply double all figures above. For a $1,500,000 target, multiply by 1.5.
How to Get to Coast FI Faster
The Coast FI number depends on three things: your retirement target, your current age, and your expected return. You have limited control over your current age and expected market returns. The retirement target is where the real leverage is.
Lower your target lifestyle in retirement. A $40,000/year retirement requires a $1,000,000 portfolio. A $60,000/year retirement requires $1,500,000. The difference in Coast FI numbers is significant. If you can plan a retirement lifestyle you would genuinely enjoy at $45,000/year rather than $65,000/year, your Coast FI number drops substantially.
Maximize early contributions. The math is unforgiving about time. $50,000 invested at age 25 is worth vastly more than $50,000 invested at age 35. The highest-value financial years are the early ones. High savings rates in the first decade of your career are disproportionately powerful because they maximize compounding years.
Minimize taxes on growth. Tax-advantaged accounts, Roth IRAs, 401(k)s, and HSAs, grow without annual tax drag. Keeping investments in tax-advantaged accounts rather than taxable brokerage accounts effectively increases your real return rate, which lowers your Coast FI number.
Control sequence of returns risk. If your portfolio experiences a significant decline just as you intend to stop contributing, your Coast FI milestone may be pushed back. Maintaining some diversification and not checking your balance obsessively during market corrections is the practical response.
Coast FI vs Other FIRE Milestones
The FIRE community uses several related terms that are worth distinguishing:
Lean FI: You have 25x your minimum acceptable annual expenses. You could retire now on a lean budget.
Coast FI: You have enough invested that compound growth reaches full FI by retirement age without additional contributions.
Barista FI / Semi-Retirement: You have enough invested to cover most expenses, but you work part-time or in a lower-income job to cover the remainder. Named after the Starbucks job many FIRE adherents take for health insurance benefits.
Fat FI: You have 25x a generous lifestyle budget. Full retirement without any lifestyle constraints.
Full FI / FIRE: 25x your actual current annual expenses. You can retire now and sustain your current lifestyle indefinitely at a 4% withdrawal rate.
Coast FI is unique because it focuses on the present value of future financial independence rather than the current ability to retire. It is a "runway" calculation rather than a "cleared for takeoff" calculation.
The Psychological Impact of Reaching Coast FI
The experience of crossing the Coast FI threshold is reported by many savers as genuinely transformative. A survey by the FIRE community at r/financialindependence consistently finds that reaching Coast FI significantly reduces financial anxiety and changes the relationship between work and money.
When you are no longer depending on your current job for your future retirement security, because that security is already locked in, the experience of work changes. You still earn to cover current expenses, but the existential pressure of "I must keep this job or my retirement is ruined" lifts. That psychological shift has practical effects: people who reach Coast FI often negotiate better at work (because they can walk away), take more risks in career development, and report higher overall life satisfaction.
Real-World Examples
Example: Jenna, 26, aggressive early saver
Situation: Jenna maxed her Roth IRA and 401(k) for three years after graduating. She has $85,000 invested. Her target retirement portfolio at 65 is $1,200,000.
Her Coast FI check: At 7% for 39 years (age 26 to 65), the present value factor is 14.97. $1,200,000 / 14.97 = $80,160 needed. She has $85,000.
Result: Jenna has already reached Coast FI at 26. Her retirement is mathematically secured by compound growth alone. She can drop to a 10% savings rate, change careers, travel, or just enjoy less financial stress for the rest of her working life.
Example: Robert, 42, starting to take FIRE seriously
Situation: Robert has $180,000 invested. He wants to retire at 67 with a $1,800,000 portfolio.
His Coast FI check: At 7% for 25 years, the present value factor is 5.43. $1,800,000 / 5.43 = $331,500 needed. He has $180,000.
His gap: $151,500 still to accumulate. At his current $1,500/month contribution and 7% return, he reaches Coast FI in approximately 5.5 years, at age 47.5.
Result: Robert is not at Coast FI yet, but he has a clear timeline. He plans to maintain aggressive saving until 48, then transition to part-time consulting while his portfolio coasts the remaining 19 years to full FI at 67.
This calculator is for educational and informational purposes only and does not constitute financial advice. Coast FI projections use assumed investment return rates and the 4% withdrawal rule. Actual investment returns are not guaranteed. Consult a licensed financial advisor for personalized retirement planning.
