Coast FIRE is the moment your investments are big enough to grow into a full retirement on their own, even if you never save another dollar. Find your number and the age you hit it.
Each week, one plain-English breakdown of the moves that get you to Coast FIRE faster: which low-cost funds to hold, how to keep fees from eating your returns, and how to stay invested when the market drops. No jargon, no spam.
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FIRE stands for Financial Independence, Retire Early. It is the idea that if you invest enough money, the returns on that money can eventually cover your living costs, so working becomes optional. Most people picture the finish line: a huge portfolio that pays for everything forever. Coast FIRE is a much earlier and friendlier milestone on the same road.
After that day, you still need a paycheck to cover rent, groceries, and life. What changes is that you no longer have to save for retirement. Compounding takes over and finishes the job for you. That can mean switching to work you actually enjoy, going part time, or simply not stressing about your 401(k) contribution every month.
Before you can know when you can coast, you need to know the size of the retirement you are aiming at. That target is your FIRE number, and there is a simple way to estimate it.
The common approach is the 4% rule. Research on historical markets found that a retiree who withdraws about 4% of their portfolio in the first year, then adjusts for inflation, has historically had a high chance of not running out of money over a 30-year retirement. Flip that around and a 4% withdrawal rate means your portfolio needs to be 25 times your annual spending.
Here is where Coast FIRE gets its power. Your FIRE number is what you need at retirement. But money invested today has years, often decades, to grow before then. So the amount you need right now to coast is much smaller than the full FIRE number.
To find it, you take your FIRE number and discount it back to today using your expected return. The longer until retirement, the smaller the Coast FIRE number, because compounding has more time to work.
| Years until retirement | Coast FIRE number today | As a share of the $1.25M goal |
|---|---|---|
| 35 years (age 30) | ~$227,000 | 18% |
| 25 years (age 40) | ~$369,000 | 30% |
| 15 years (age 50) | ~$601,000 | 48% |
| 5 years (age 60) | ~$979,000 | 78% |
This table assumes a $1.25M FIRE number and a 5% after-inflation return. Notice the pattern: a 30-year-old needs less than one-fifth of the full goal invested today to coast. Time is doing the heavy lifting. This is exactly why starting early matters so much, and why Coast FIRE is the most reachable FIRE milestone for younger investors.
FIRE is not one thing. The label in front tells you how much you are aiming for and how you plan to get there.
| Type | What it means | Still need a job? |
|---|---|---|
| Coast FIRE | Retirement is already funded by future growth; you stop saving but keep working to pay today's bills. | Yes, for current costs only |
| Barista FIRE | Part-time or lower-stress work covers some expenses while your portfolio covers the rest. | Partly |
| Lean FIRE | Full financial independence on a modest, frugal budget. | No |
| Regular FIRE | Full financial independence at a comfortable, typical spending level. | No |
| Fat FIRE | Full financial independence with a generous, high-spending lifestyle. | No |
Coast FIRE sits at the front of this list because it asks the least of you up front. You are not trying to fund your entire life from investments. You are just trying to get retirement off your to-do list early.
This calculator asks for your return after inflation, also called a real return, and that choice matters. Your retirement spending is set in today's dollars: $50,000 a year means $50,000 of today's buying power. If you projected your portfolio using a nominal return that includes inflation, you would be comparing future inflated dollars against a today's-dollars goal, and your Coast FIRE number would look smaller than it really is.
Using a real return keeps both sides in the same units. A broad U.S. stock index has returned roughly 7% after inflation over the long run. A blend of stocks and bonds lands closer to 4 to 5%, which is why 5% is a reasonable middle-of-the-road default here. To see how those returns build a balance over time, the investment calculator shows the year-by-year compounding in detail.
Coast FIRE is a useful milestone, not a guarantee. A few honest caveats:
It depends on returns showing up. The math assumes your money earns its expected return every year. Real markets do not work that way. A long stretch of weak returns early on can leave you short, so it is worth rechecking your number every few years rather than declaring victory and never looking again.
It does not fund early retirement. Coast FIRE funds retirement at the age you set, not before. If you stop working entirely at 45, your money is still locked into growing until your target age, so you would need a separate plan for the years in between.
Your spending estimate has to hold. Healthcare, housing, and lifestyle changes can move your real retirement spending well away from today's guess. A higher spending number means a higher FIRE number and a higher Coast FIRE number.
Fees still matter. Every projection here is before investment fees. A high expense ratio quietly lowers your real return, which pushes your Coast FIRE date later. Keeping costs low with broad index funds is one of the few levers fully in your control. Our guide to expense ratios covers what counts as reasonable, and the fee calculator shows the dollar cost over time.
It runs three calculations. First, it turns your annual spending and withdrawal rate into a FIRE number (spending divided by withdrawal rate). Second, it discounts that FIRE number back to today using your after-inflation return and the years until retirement, which gives your Coast FIRE number for today. Third, it grows your current investments and monthly contributions forward month by month, and finds the first age at which your portfolio is large enough to coast the rest of the way on its own. That crossover age is the point you can stop saving. Everything is before fees and taxes, which depend on your accounts and are not modeled here.
Educational purposes only. This calculator illustrates the mathematics of Coast FIRE based on the inputs you provide. It does not constitute financial advice, investment recommendations, or personalized guidance. Projections are hypothetical and assume a constant annual return, which real markets do not deliver. The 4% rule is a historical guideline, not a guarantee, and sequence-of-returns risk can change outcomes. Results exclude fees and taxes. ETF BFF is not a registered investment advisor. Past performance does not guarantee future results. Always do your own research and consider consulting a qualified financial professional before making investment decisions.