Coast FIRE Calculator
Estimate your Coast FIRE number, see if you are already there, and project your portfolio at retirement in today's dollars.
What Is Coast FIRE?
Coast FIRE is a form of financial independence where you have already invested enough that, if left alone to compound, your portfolio should grow to your full retirement target by the time you retire. In plain English: once you hit Coast FIRE, your future retirement is mostly funded by time and market growth, not by aggressive new savings.
People who reach Coast FIRE often feel a huge sense of flexibility. You may choose to keep working, but with less pressure. You might shift to part-time work, start a business, move to lower-stress roles, or simply enjoy spending a bit more now while staying on track for traditional retirement.
How This Coast FIRE Calculator Works
1) It calculates your FIRE number
Your FIRE number is the portfolio size needed to support your retirement spending. The calculator uses the classic rule:
- FIRE number = annual spending ÷ withdrawal rate
Example: If you plan to spend $60,000 per year and use a 4% withdrawal rate, your FIRE number is $1.5 million.
2) It discounts that target back to today
The tool then estimates your required portfolio today (your Coast FIRE number) using your expected real return, which is investment return adjusted for inflation.
- Real return ≈ (1 + return) ÷ (1 + inflation) - 1
- Coast FIRE today = FIRE number ÷ (1 + real return)years to retirement
If your current invested assets are above that Coast FIRE number, you are already at Coast FIRE.
3) It projects your retirement balance
The calculator also projects your portfolio at retirement based on your current balance and monthly contributions. That gives you context: even if you are not at Coast FIRE yet, you can see how close you are and what your trajectory looks like.
Input Guide: What to Enter
- Current age / retirement age: Defines your compounding window.
- Current invested portfolio: Retirement accounts, brokerage accounts, and other long-term investments.
- Monthly contribution: Amount you regularly invest until retirement.
- Target annual retirement spending: Estimated yearly expenses in retirement, in today's dollars.
- Safe withdrawal rate (SWR): 4% is common; conservative plans may use 3.5% or lower.
- Expected annual return and inflation: Used to estimate real growth over time.
How to Interpret Your Results
If you are already Coast FIRE
That means your current portfolio is large enough to reach your full FIRE number by retirement with no new contributions (assuming your return assumptions hold). You can still invest, of course, but you now have optionality.
If you are not yet Coast FIRE
The result shows your gap. That gap is often smaller than people expect, especially if retirement is decades away. Time is the most powerful input in a Coast FIRE plan.
Watch the assumptions
Every calculator is a model, not a guarantee. Markets are volatile, inflation varies, and spending can shift. Use this as a planning tool and rerun it periodically as your life and numbers change.
Practical Ways to Reach Coast FIRE Faster
- Automate investing: Consistency usually beats perfect timing.
- Increase income strategically: Promotions, skill development, or side income can accelerate contributions.
- Lower your required retirement spending: Even modest reductions can significantly reduce your FIRE number.
- Control lifestyle inflation: Raise savings rate with each income increase.
- Optimize fees and taxes: Lower drag can materially improve long-term compounding.
Coast FIRE vs. Other FIRE Paths
Traditional FIRE
You save aggressively until your portfolio can fully cover your expenses immediately.
Coast FIRE
You front-load investing, then let compounding finish the job while your current work covers your living costs.
Barista FIRE
You partially retire and use part-time income to cover some expenses and often healthcare, reducing withdrawal needs.
Lean FIRE / Fat FIRE
Lean FIRE targets lower spending and smaller portfolios; Fat FIRE targets higher spending and larger portfolios. Coast FIRE can be used on either path.
Common Mistakes to Avoid
- Using overly optimistic return assumptions.
- Ignoring inflation and taxes.
- Forgetting to update spending estimates after major life changes.
- Treating a single projection as certainty.
Final Thought
The biggest value of a Coast FIRE calculator is not just the number. It is clarity. Once you understand where you stand, you can make intentional choices about work, spending, and lifestyle. Run the math, revisit it regularly, and use it to design a life that balances future security with present-day meaning.