How to Calculate Your Coast FIRE Number
Find the portfolio balance where your money grows to your FIRE number without new contributions.
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Finance & Investment
Coast FIRE Calculator 2026
Free Coast FIRE calculator to find your coast fire number: the amount you need invested today so compound growth alone reaches your retirement goal. Works for couples, supports pension and Social Security adjustments, and shows the exact age you coast.
Free, no sign-up
Works for couples
Pension and Social Security support
Financial Disclaimer: This calculator is for informational purposes only. It is not financial advice. Consult a licensed financial advisor before making retirement or investment decisions.
How to Calculate Your Coast FIRE Number: Formula, Steps, and a Worked Example
To find your coast fire number, the calculator works backward from your retirement goal. First it finds the retirement corpus you need: annual expenses divided by your withdrawal rate. Then it discounts that corpus back to today at your expected return rate. The result is the savings balance at which compound growth alone handles the rest. Maximizing a Roth IRA in your 20s and 30s is one of the most efficient ways to hit that number, since contributions compound tax-free for decades.
The Coast FIRE Formula
Retirement Corpus = Annual Expenses / Withdrawal Rate
Coast FIRE Number = Corpus / (1 + Return)^Years to Retirement
Already Coasted?= Current Savings >= Coast FIRE Number
Coast FIRE Number = Corpus / (1 + Return)^Years to Retirement
Already Coasted?= Current Savings >= Coast FIRE Number
Withdrawal Rate Options
- 4% rule (25x expenses): the classic Trinity Study benchmark for a 30-year retirement
- 3.5% rule (28.6x expenses): more conservative, better for early or very long retirements
- 5% rule (20x expenses): aggressive, with higher risk of running short in a down market
Worked Example: Priya at Age 34
Priya is 34, plans to retire at 60, wants $65,000/year in retirement, has $110,000 saved, and assumes 7% growth with the 4% withdrawal rule.
Retirement corpus ($65,000 / 4%)$1,625,000
Years to retirement (60 minus 34)26 years
Coast FIRE ($1,625,000 / 1.07^26)$277,400
Current savings$110,000
Gap to coast-$167,400
Saving $15,000/yr, coasts at age40
Once Priya hits Coast FIRE at 40, she can stop retirement contributions entirely. Her $277,400 grows to $1.625M by age 60 through compound returns alone. For many households, clearing high-interest debt with a debt snowball plan frees up the cash flow needed to reach that coast number faster.
Coast FIRE Numbers by Age: What You Need at 25, 30, 35, and 40
The earlier you start, the smaller your coast fire number is. Compound growth does more work when it has more years. At 25 with 35 years to a retirement at 60, you need less than $100,000 to coast to a $1 million corpus. By 40, that same target requires over $250,000. The table below assumes a 7% annual return, a 4% withdrawal rate, and retirement at age 60.
| Current Age | Years to 60 | $40k/yr expenses | $60k/yr expenses | $80k/yr expenses |
|---|---|---|---|---|
| 25 | 35 | $94,000 | $141,000 | $188,000 |
| 30 | 30 | $131,000 | $197,000 | $263,000 |
| 35 | 25 | $184,000 | $276,000 | $368,000 |
| 40 | 20 | $258,000 | $388,000 | $517,000 |
| 45 | 15 | $362,000 | $544,000 | $725,000 |
| 50 | 10 | $508,000 | $763,000 | $1,017,000 |
Assumes 7% annual return, 4% withdrawal rate, retirement at age 60. Coast FIRE number = (annual expenses x 25) / (1.07^years to retirement).
These numbers drop considerably if you use a 3.5% withdrawal rate (more conservative) or a later retirement age. Run the calculator above with your specific assumptions to get a precise number for your situation.
Coast FIRE vs Barista FIRE: Two Paths Out of Full-Time Work
Both strategies let you stop saving aggressively for retirement before traditional retirement age, but they get there through different mechanics. Coast FIRE uses portfolio size alone. Barista FIRE relies on a combination of a smaller portfolio and ongoing part-time income. Which one gets you there faster depends on your current balance, your savings rate, and whether you are willing to keep working part-time.
| Attribute | Coast FIRE | Barista FIRE |
|---|---|---|
| Portfolio required | Larger (covers full corpus growth) | Smaller (only covers expense gap) |
| Earned income after milestone | Not required | Required, part-time ongoing |
| Stop making contributions? | Yes | Yes |
| Reach milestone sooner? | Requires more saved first | Yes, due to income offset |
| Health insurance source | ACA or out of pocket | Employer (20+ hrs) or ACA |
| Key risk | Market growth falls short | Part-time income disappears |
| Best fits | Those who want full freedom sooner | Those comfortable with part-time work |
Some people reach Coast FIRE first, then transition to part-time work while the portfolio grows toward full FIRE. That layered approach combines the strengths of both strategies. Use the Barista FIRE Calculator to see how much part-time income would reduce your required portfolio, and compare that timeline to your coast number above.
What Counts Toward Your Coast FIRE Number: Accounts, Pensions, and Social Security
Your coast fire number is a portfolio balance, not a net worth figure. What you include in "current savings" matters significantly, and not every asset belongs in the calculation.
What to Include
401k / 403b / 457 (traditional and Roth)
Full balance counts. These grow tax-sheltered until retirement.
IRA and Roth IRA
Full balance counts. Roth contributions can be withdrawn early, but for coast FIRE purposes include the full invested balance.
Taxable brokerage accounts
Include invested assets (stocks, ETFs, mutual funds). Do not include cash sitting in a savings account.
HSA balance (invested portion)
If your HSA funds are invested in funds rather than sitting in cash, they count toward long-term growth.
Do Not Include
Home equity, emergency fund cash, 529 college savings, and illiquid assets like rental property equity do not belong in your coast FIRE balance. The coast number assumes liquid, market-invested assets growing at your expected return rate.
Adjusting for Pensions and Social Security
Both reduce what your portfolio must fund. Subtract expected annual income from your annual expenses input before running the calculation. If you plan to spend $70,000 per year and your pension pays $22,000 annually, enter $48,000 as annual expenses. Your coast number drops from $471,000 to $325,000 at age 35 with a 25-year runway (7% return, 4% withdrawal).
Federal employees with FERS benefits can estimate their pension using the FERS Retirement Calculator before entering their adjusted expense figure here.
Common Mistakes to Avoid
Using nominal returns instead of real returns
A 10% nominal return with 3% inflation is a 7% real return. Using 10% overstates your portfolio's purchasing power at retirement and makes your coast number look smaller than it actually is.
Forgetting taxes on withdrawals
Traditional 401k and IRA withdrawals are taxed as ordinary income. Your gross corpus target should be higher to cover the tax hit if most savings are in pre-tax accounts.
Ignoring sequence-of-returns risk
A bad market in the first few years of retirement can derail even a well-funded plan. A 3.5% withdrawal rate provides more cushion than 4% and is worth the higher coast number.
Counting only retirement accounts
Taxable brokerage accounts count toward your coast FIRE balance. Include all long-term invested assets, not just 401k and IRA balances, since they all compound over time.
Thinking Coast FIRE means you stop saving entirely
Coast FIRE means your portfolio will grow to your target without additional contributions. You still need income to cover living expenses until retirement. Many people keep contributing to retire earlier or build a bigger cushion.
Frequently Asked Questions
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Sources & References
1
Bengen, W. (1994): Determining Withdrawal Rates Using Historical Data
Journal of Financial Planning. Original source for the 4% withdrawal rate rule and its 30-year sustainability basis.
2
Cooley, Hubbard, Walz (1998): Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable
The Trinity Study. Provides empirical success rates for various withdrawal rates across historical market cycles.
3
Vanguard (2023): How America Saves. Annual Defined Contribution Plan Data
Source for median 401(k) balance data by age bracket, used to contextualize Coast FIRE progress relative to typical American retirement savings rates.
HR
Hassaan Rasheed
Developer and Researcher, CalculatorFlux
Researches and verifies the formulas, methodology, and source data behind each calculator on CalculatorFlux. All tools are built and checked against the cited references before publication.
Last updated: June 2026