Calculate Your Coast FI Number
Use this tool to estimate whether your current portfolio can grow on its own to fund retirement, even if you stop contributing today.
What Is Coast FI?
Coast FI means you have invested enough money today that, if left to grow without any new contributions, it should reach your retirement target by your planned retirement age. In plain language: once you hit Coast FI, your future retirement is mostly powered by time and compounding.
Many people like Coast FI because it creates flexibility. You can reduce work hours, switch careers, start a business, or focus on meaningful projects without feeling like you are falling behind forever.
How This Coast FI Calculator Works
Step 1: Estimate your retirement target
The calculator starts with your estimated annual retirement spending and your safe withdrawal rate. A common framework is:
- Target portfolio = Annual spending / Withdrawal rate
- Example: $60,000 per year with a 4% withdrawal rate implies about $1,500,000.
Step 2: Discount that target back to today
Next, it calculates how much you would need invested now so your money can compound up to that target by retirement:
- Coast FI number today = Target portfolio / (1 + real return)^(years to retirement)
If your current invested assets are above that number, you are already Coast FI.
Step 3: Show your contribution gap (if any)
If you are not Coast FI yet, the calculator also estimates how much you may need to save each year (or month) to reach your retirement target by your chosen age.
Input Guide: What to Enter
- Current age: Your age today.
- Planned retirement age: The age when you want work to become optional.
- Current invested portfolio: Retirement and taxable investments earmarked for retirement.
- Annual retirement spending: Your expected yearly spending in today’s purchasing power.
- Safe withdrawal rate: Many use 4%; conservative planners may use 3.5%.
- Expected real return: Return after inflation. Long-term planning often uses 4% to 6% real.
Example Scenario
Suppose you are 32, plan to retire at 60, have $175,000 invested, want $60,000 per year in retirement spending, use a 4% withdrawal rate, and expect 5% real returns.
- Your retirement target is about $1.5 million.
- Your Coast FI number today is much lower because you have 28 years to compound.
- The calculator shows whether $175,000 already clears that threshold.
If yes, you can theoretically stop retirement contributions and still be on track. If not, the required monthly contribution provides a practical next step.
How to Reach Coast FI Faster
1) Focus on savings rate first
Consistent investing usually matters more than trying to outguess markets. Automate transfers on payday and avoid lifestyle inflation when income rises.
2) Keep fees and taxes low
Lower expense ratios, low-turnover index funds, and tax-efficient account placement can improve long-term compounding.
3) Protect downside risk
Emergency savings and adequate insurance reduce the chance of tapping investments early, which can delay your Coast FI timeline.
4) Revisit assumptions annually
Spending, markets, and life plans change. Re-running your numbers once or twice each year helps keep the plan realistic.
Common Coast FI Mistakes
- Using nominal returns while also assuming future spending in today's dollars.
- Ignoring healthcare and taxes in retirement spending estimates.
- Choosing an unrealistically high expected return.
- Assuming one fixed retirement age with no backup scenario.
Final Thoughts
Coast FI is less about quitting work tomorrow and more about buying options. Once your future is largely funded, you gain the freedom to design a life that fits your values now. Use the calculator above, stress-test your assumptions, and build a plan that is both ambitious and resilient.