Coast FIRE Calculator — Find Your CoastFIRE Number
Coast FIRE Number
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Years to Grow
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How Coast FIRE Works
Coast FIRE (Financial Independence, Retire Early) is the point at which you have invested enough money that compound growth alone will grow your portfolio to your target retirement number by your desired retirement age, even if you never save another dollar. Once you reach Coast FIRE, you still need to earn enough to cover your current living expenses, but you no longer need to contribute to retirement accounts. The concept was popularized within the FIRE movement community and draws on the mathematical principle of compound growth described in Investopedia's compound interest guide.
Coast FIRE is especially appealing to younger workers in their 20s and 30s who want to transition from high-income, high-stress careers to lower-paying but more fulfilling work. A 2024 Bankrate survey found that 55% of American workers feel they are behind on retirement savings. Coast FIRE reframes the question: instead of "How much do I need to save every month until retirement?" it asks "How much do I need to save right now so that compound growth does the rest?" For someone age 30 targeting $1.5 million at age 65, the Coast FIRE number at a 7% real return is approximately $140,000 -- a target that feels achievable compared to the full $1.5 million.
The Coast FIRE Formula
The Coast FIRE formula calculates the present value of your target retirement portfolio, discounted by expected compound growth over the remaining years until retirement:
Coast FIRE Number = FIRE Number / (1 + r)^n
Where:
- FIRE Number: Your target portfolio value at retirement (typically 25x your annual expenses, based on the 4% safe withdrawal rate)
- r: Expected annual real (inflation-adjusted) rate of return (commonly 7%)
- n: Number of years until your target retirement age
Worked example: A 30-year-old targets $1,500,000 at age 65 with a 7% expected return. Coast FIRE Number = $1,500,000 / (1.07)^35 = $1,500,000 / 10.677 = approximately $140,500. If this person currently has $100,000 saved, they need an additional $40,500 to reach Coast FIRE. Once they hit $140,500, compound growth alone will carry them to $1.5 million by age 65, assuming 7% average annual returns. You can model the growth trajectory using our compound interest calculator.
Key Terms You Should Know
- FIRE Number: The total amount you need invested to live off your portfolio indefinitely. Calculated as 25 times your annual expenses (based on the 4% rule). If you spend $60,000/year, your FIRE number is $1,500,000.
- Safe Withdrawal Rate (SWR): The percentage of your portfolio you can withdraw annually without running out of money over a 30-year retirement. The Trinity Study established 4% as the standard SWR. Use our safe withdrawal rate calculator to test different scenarios.
- Compound Growth: The process by which investment returns generate their own returns over time. A 7% annual return doubles your money approximately every 10.3 years (using the Rule of 72: 72/7 = 10.3 years).
- Real vs. Nominal Returns: Nominal returns are before inflation adjustment. Real returns subtract inflation. The S&P 500 has returned approximately 10% nominal and 7% real (after 3% average inflation) since 1926.
- Barista FIRE: A variation of Coast FIRE where you work a part-time job specifically for health insurance benefits while your portfolio grows. Named after the idea of working at Starbucks, which provides health insurance to part-time employees working 20+ hours per week.
- Sequence of Returns Risk: The risk that poor investment returns early in retirement will deplete your portfolio faster than average returns suggest. This risk is why maintaining a buffer above your Coast FIRE number is prudent.
Coast FIRE Numbers by Age and Target
The table below shows the Coast FIRE number needed at various ages to reach a $1,500,000 portfolio by age 65, assuming a 7% real annual return. The younger you are, the lower your Coast FIRE number because compound growth has more time to work. Data is derived from the present value formula and historical S&P 500 real return averages since 1926.
| Current Age | Years to 65 | Coast FIRE (7%) | Coast FIRE (5%) | Coast FIRE (9%) |
|---|---|---|---|---|
| 25 | 40 | $100,250 | $213,150 | $47,800 |
| 30 | 35 | $140,500 | $271,950 | $73,350 |
| 35 | 30 | $197,050 | $347,050 | $112,600 |
| 40 | 25 | $276,250 | $442,800 | $173,850 |
| 45 | 20 | $387,400 | $565,050 | $267,650 |
| 50 | 15 | $543,300 | $721,100 | $411,650 |
Practical Examples
Example 1 -- Young Professional: Priya is 28, earns $75,000 per year, and has $95,000 in her 401(k) and Roth IRA combined. Her annual expenses are $50,000, giving her a FIRE number of $1,250,000 (25 x $50,000). At 7% real return with retirement at 65 (37 years away), her Coast FIRE number is $1,250,000 / (1.07)^37 = approximately $101,000. She has already surpassed her Coast FIRE number. She could stop all retirement contributions today and her portfolio would still grow to $1.25 million by age 65. This frees her to consider a career change to a lower-paying but more fulfilling role.
Example 2 -- Mid-Career Pivot: James is 40, has $220,000 saved, and targets $2,000,000 at age 60 (a more ambitious FIRE number because he lives in a high-cost area). His Coast FIRE number at 7% over 20 years = $2,000,000 / (1.07)^20 = approximately $516,850. He is $296,850 short. At his current savings rate of $30,000 per year with 7% growth, he would reach his Coast FIRE number in approximately 7 years at age 47. He can use the retirement calculator to model different contribution scenarios.
Example 3 -- Conservative Planner: Maria is 35 with $180,000 saved, targeting $1,500,000 at age 65. Using a conservative 5% return (to account for a bond-heavy portfolio), her Coast FIRE number = $1,500,000 / (1.05)^30 = approximately $347,050. She needs $167,050 more. At 7% return, the number drops to $197,050, meaning she is only $17,050 short. The difference between 5% and 7% assumptions is dramatic -- nearly $150,000 -- illustrating why the return rate assumption is the most sensitive variable in Coast FIRE calculations.
Tips and Strategies for Coast FIRE
- Start early and front-load savings: The power of Coast FIRE comes from time. A dollar invested at age 25 has 40 years to compound before age 65. At 7% real returns, that dollar grows to approximately $15. Maximizing savings in your 20s and early 30s makes reaching Coast FIRE dramatically easier.
- Use conservative return assumptions: While 7% real return is the standard assumption, planning with 5% to 6% provides a safety margin. If the market delivers 7%, you reach your target early. If it delivers 5%, you still hit your number.
- Maintain a 10-20% buffer: Do not stop contributions the moment you hit your exact Coast FIRE number. Market volatility means your portfolio could drop 20% to 30% in a bad year. A buffer ensures you stay on track even after a downturn.
- Plan for healthcare costs: If you leave a full-time job with employer health insurance, budget for marketplace insurance premiums ($400 to $800 per month for an individual in 2024). This is the biggest expense gap between Coast FIRE and traditional employment.
- Reassess annually: Recalculate your Coast FIRE number every year using your actual portfolio balance, updated return assumptions, and any changes to your target FIRE number or retirement age. Life changes, inflation, and market performance all affect the calculation.
- Consider tax-advantaged accounts: Keep investing in Roth IRA or Roth 401(k) even after reaching Coast FIRE if your income is low enough. Tax-free growth and withdrawals in retirement are especially valuable over long time horizons. Use our Roth conversion calculator to evaluate conversion strategies.
Frequently Asked Questions
What investment return rate should I use for Coast FIRE calculations?
A 7% inflation-adjusted return rate is the most commonly used assumption, based on the S&P 500's historical average annual return of approximately 10% minus 3% average inflation. For more conservative planning, use 5% to 6% to account for potentially lower future returns or a portfolio that includes bonds. If your portfolio is heavily weighted toward bonds or international equities, a lower rate of 4% to 5% may be more realistic.
Is Coast FIRE the same as regular FIRE?
No. Regular FIRE means your portfolio is large enough to cover all living expenses indefinitely through withdrawals at a 4% annual rate. Coast FIRE means you have saved enough that compound growth alone will grow your portfolio to your retirement target, even if you never contribute again. After reaching Coast FIRE, you still need employment income for current expenses, but you no longer need to save for retirement.
What if the stock market crashes after I reach Coast FIRE?
A significant market downturn could push your portfolio below your Coast FIRE number. Maintain a 10% to 20% buffer above the calculated number before stopping contributions. Recalculate annually using your actual portfolio balance. If a crash occurs, you may need to resume contributions temporarily until your portfolio recovers. The longer your time horizon to retirement, the more time for recovery.
How much do I need to reach Coast FIRE by age 30?
Assuming a $1.5 million FIRE number at age 65 with 7% annual returns over 35 years, you would need approximately $140,500 saved by age 30. If you target age 60, you would need about $197,050. Starting early is powerful because compound growth does most of the work over 30 to 35 years. Use our compound interest calculator to see how different starting amounts grow over time.
What is the difference between Coast FIRE and Barista FIRE?
Coast FIRE means your existing investments will grow to your retirement target through compound growth alone, so you only need to earn enough for current expenses. Barista FIRE is a related concept where you work a part-time job specifically for health insurance benefits while your portfolio grows. The name comes from the idea of working at Starbucks, which offers health insurance to part-time employees working 20+ hours per week. Both strategies enable leaving high-stress careers earlier than traditional retirement.
Does Coast FIRE account for inflation?
Coast FIRE calculations should use inflation-adjusted (real) returns to produce a target in today's purchasing power. Using a 7% return rate already accounts for approximately 3% annual inflation (10% nominal minus 3% inflation). If you use the nominal 10% return without adjusting, your Coast FIRE number will appear lower but your FIRE number at retirement will have less purchasing power than expected. Always verify whether your target FIRE number is in today's dollars or future nominal dollars.