Coast FIRE Calculator
When can you stop saving and let compound growth carry you to retirement?
How This Calculator Works
Runs in your browser. No account. No saved financial data.
Formula
Coast FIRE number is the present value of your full FIRE number: FIRE number / (1 + real return)^years.
The calculator also searches year by year for the age when your projected savings cross that year's coast threshold.
Worked example
A $1,000,000 FIRE target, 4.39% real return, and 25 years until retirement produces a coast number of about $341,600. If you have more than that today, growth alone can carry the retirement target.
Assumptions
- Retirement spending is converted into a full FIRE number first.
- Coast-only balance means no future contributions after today.
- Active-saving balance includes your annual contributions until the selected retirement age.
Limits
- The model assumes a constant real return rather than volatile yearly markets.
- It does not model taxes, fees, Social Security, pensions, or future spending changes.
- Coast FIRE is a milestone, not a recommendation to stop saving.
Coast FIRE number needed today (for a $1M FIRE target)
Each cell is the present value of a $1M FIRE target — the lump sum that, with no further contributions, compounds to $1M by retirement. Rows are years until retirement; columns are real (inflation-adjusted) return assumptions.
| Years until retirement | 3% real return | 4% real return | 5% real return | 6% real return |
|---|---|---|---|---|
| 10 years | $744k | $676k | $614k | $558k |
| 15 years | $642k | $555k | $481k | $417k |
| 20 years | $554k | $456k | $377k | $312k |
| 25 years | $478k | $375k | $295k | $233k |
| 30 years | $412k | $308k | $231k | $174k |
| 35 years | $355k | $253k | $181k | $130k |
Scale linearly for other targets — a $2M FIRE goal doubles every cell. Time and real return are the dominant levers: an extra 10 years of runway can cut the required Coast number by more than half.
What Coast FIRE Means
Coast FIRE is the point where your current investments can compound to your full retirement target by your chosen retirement age without any additional contributions. You are not financially independent today; you still need income for current living expenses. The difference is that retirement savings no longer has to be the main job of every paycheck. That can create room for lower-stress work, part-time work, career changes, entrepreneurship, parenting, travel, or simply a less aggressive savings rate.
Coast FIRE sits between traditional accumulation and full FIRE. Regular FIRE means your portfolio can support current spending now. Barista FIRE usually means the portfolio covers part of spending while work covers the rest, often with benefits. Coast FIRE means the portfolio is large enough for the future target, but not for today's spending. This calculator focuses on that compounding threshold so you can see whether you are already ahead of schedule or how many more years of saving may be required.
Coast FIRE Formula and Examples
The formula is FIRE number ÷ (1 + real return)years until retirement. If your full FIRE number is $1,500,000, you have 30 years until retirement, and you assume a 5% real return, the Coast FIRE number is about $347,000. At 25 years, it rises to about $443,000. At 20 years, it is about $566,000. The shorter the compounding runway, the more you need today.
| Age today | Retirement age | Years to compound | Coast number for $1.5M target at 5% real |
|---|---|---|---|
| 30 | 65 | 35 | About $272,000 |
| 35 | 65 | 30 | About $347,000 |
| 40 | 65 | 25 | About $443,000 |
These examples are sensitive to the real return assumption. A lower return means a higher Coast FIRE number. A later retirement age gives compounding more time. A higher spending target increases the full FIRE number and therefore the coast threshold. If you are unsure about the withdrawal rate behind the target, start with the FIRE number calculator, then test the withdrawal plan with the safe withdrawal rate calculator.
Can You Stop Saving After Coast FIRE?
Mathematically, Coast FIRE says additional retirement contributions are not required under the assumptions entered. Practically, stopping all saving can be risky if your assumptions are optimistic or your life changes. A more resilient approach is to use Coast FIRE as a pressure-release valve. You might reduce contributions, keep employer matches, fund tax-advantaged accounts when income is high, or redirect some savings toward cash reserves, debt payoff, education, or a business runway.
Coast FIRE is most useful when it changes decisions without pretending risk disappeared. Markets can underperform. Inflation can run hot. Retirement spending can rise. Taxes can change. A conservative planner reruns the coast calculation every year, uses a range of real returns, and avoids treating one green result as permission to ignore the rest of the financial plan.
Sources & References
The Coast FIRE threshold relies on a FIRE target produced by the same SWR research used elsewhere on this site. Real-return assumptions are calibrated against historical equity data (FRED) and CPI inflation.
- Determining Withdrawal Rates Using Historical Data — William P. Bengen, Journal of Financial Planning (1994)
Origin of the 4% rule. Tests fixed real-dollar withdrawals against U.S. equity and bond returns from 1926.
- Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable — Cooley, Hubbard, Walz — Trinity University (1998, AAII Journal)
Trinity Study. Reports portfolio success rates for 15–30 year retirements at withdrawal rates from 3% to 12%.
- S&P 500 Index — FRED — Federal Reserve Bank of St. Louis
Public S&P 500 series. Used when articles report long-run U.S. equity return averages.
- Consumer Price Index (CPI-U) — U.S. Bureau of Labor Statistics
Headline CPI series. Default inflation assumptions in calculators are calibrated against long-run CPI averages.
- Retirement Topics — IRA Contribution Limits — Internal Revenue Service
Annual IRA and 401(k) contribution limits used in savings-rate and FIRE-projection articles.
Frequently Asked Questions
What is Coast FIRE?
Coast FIRE means you've saved enough that compound growth alone will grow your portfolio to your full FIRE number by retirement age — without any additional contributions. You still work, but only to cover current expenses.
How is Coast FIRE different from regular FIRE?
Regular FIRE means you can stop working entirely. Coast FIRE means you've saved enough that you can stop saving — your existing investments will compound to your target. You still need income for current expenses.
What does the Coast FIRE Age mean?
It's the age at which your current savings (plus projected contributions) will have crossed the threshold where growth alone carries you to your retirement target. After this age, additional savings aren't mathematically necessary.
Should I actually stop contributing at Coast FIRE?
Coast FIRE is a milestone, not necessarily a prescription. Many people use it to reduce financial pressure — switching to lower-stress work, going part-time, or pursuing passion projects while knowing retirement is secured.