What is Coast FIRE?
Coast FIRE is the point where the money you've already invested is enough to grow, by itself, into a full retirement portfolio by your chosen retirement age. Once you reach it, you no longer need to save for retirement. You still need to earn enough to pay your current bills, but you could switch to a lower-paying job you enjoy, work part-time, or take a sabbatical while your investments "coast" to the finish line.
It's a milestone on the way to FIRE (Financial Independence, Retire Early), and for many people it's the more realistic and more motivating goal: it usually arrives a decade or more before full financial independence.
How this calculator works
The calculator does three things, all in today's dollars so the numbers are easy to compare with your current life:
- Your FIRE number. The portfolio you need at retirement to fund your yearly spending at your chosen withdrawal rate.
- Your Coast FIRE number. How much you need invested today for that FIRE number to be reached by compound growth alone.
- Your Coast FIRE age. If you're not there yet, it simulates your portfolio month by month with your contributions and finds the first month where your balance catches up with the (rising) Coast FIRE target.
The formulas
FIRE number = yearly spending ÷ withdrawal rate
Coast FIRE number = FIRE number ÷ (1 + r)years to retirement
Using a real (inflation-adjusted) return is what keeps everything in today's dollars. A 7% nominal return with 3% inflation is a real return of about 3.88%, not 4%, because the two compound together.
Worked example
Say you're 30, want to retire at 60 and expect to spend $40,000 a year. At a 4% withdrawal rate your FIRE number is $40,000 ÷ 0.04 = $1,000,000. With a 7% return and 3% inflation (3.88% real), your Coast FIRE number is $1,000,000 ÷ 1.038830 ≈ $318,900.
So if you had about $319,000 invested at 30, you could stop contributing entirely and, under these assumptions, still have roughly $1 million in today's money at 60. If you have $100,000 today and stop saving, you'd reach only about $314,000, a big gap, which is why the calculator also shows how long continued contributions take to close it.
How to use your result
- Stress-test it. Open Assumptions and try a 6% return or a 3.5% withdrawal rate. If you'd still be close to Coast FIRE under conservative numbers, your plan is robust.
- Watch the gap, not just the number. The Coast FIRE target rises every year you get closer to retirement (there's less time left to compound), so the line you're chasing slopes upward on the chart.
- Keep the match. Even after you hit Coast FIRE, contributing enough to get a full employer match is usually free money.
- Mind the account types. Money in 401(k)s and IRAs may be locked until 59½. If you plan to retire earlier, you'll need taxable savings or a withdrawal strategy (such as a Roth conversion ladder) to bridge the gap.
Limitations
Markets don't deliver a smooth average return. A bad decade early on can delay your timeline even if the long-run average holds. The calculator also ignores taxes on withdrawals and fees. Treat the result as a planning range, revisit it once a year, and consider talking to a fee-only financial planner before making big career decisions based on it.
Frequently asked questions
What is the difference between Coast FIRE and regular FIRE?
With regular FIRE you have enough invested to stop working entirely and live off your portfolio now. With Coast FIRE you have enough invested that you can stop saving for retirement: you still work to cover today's expenses, but your existing portfolio grows to your full retirement number on its own by your target age.
What return and inflation should I use?
Many planners use a long-run nominal stock return of 6–8% and inflation of 2.5–3.5%, which gives a real return of roughly 3–5%. A more conservative assumption (for example 6% return and 3% inflation) produces a higher, safer Coast FIRE number. Past returns don't guarantee future results.
Is the 4% rule still valid?
The 4% rule comes from historical US data over 30-year retirements. For early retirees with 40+ year horizons, many people use 3.25–3.75% to add a margin of safety. Lowering the withdrawal rate raises your FIRE number and therefore your Coast FIRE number.
Does this include Social Security or a pension?
No. If you expect Social Security, a pension or rental income, subtract that yearly amount from your retirement spending before entering it. That reduces the amount your portfolio needs to cover.
Should I really stop contributing once I hit Coast FIRE?
You can, but many people keep contributing a little, especially to capture an employer 401(k) match. Extra contributions are a buffer against poor markets, and they let you retire earlier than your target age.
Sources
- Determining Withdrawal Rates Using Historical Data (W. P. Bengen, 1994), Journal of Financial Planning, via the Financial Planning Association
- Consumer Price Index (CPI), U.S. Bureau of Labor Statistics
- Topic no. 557, Additional tax on early distributions from traditional and Roth IRAs, Internal Revenue Service
This calculator is for educational purposes and gives estimates based on the numbers you enter. It is not financial, tax or legal advice. Last reviewed October 2026.