Coast FIRE Calculator
Find your Coast FIRE number and the exact age you can stop saving — the moment your invested money will compound to your retirement target on its own. Instant, no sign-up, formula shown.
Quick answer
If you are 30, plan to retire at 60 and expect to spend $40,000 a year, your FIRE number is $1,000,000 and your Coast FIRE number today is about $318,862. Reach that, and you could stop saving for retirement entirely and still arrive on target — assuming a 7% return against 3% inflation. Change the inputs above and this answer updates with your own numbers.
The moment you hit Coast FIRE
Green is your portfolio; indigo is the Coast FIRE target (it rises toward your FIRE number as retirement nears). Where green crosses indigo, you can stop saving.
How your monthly contribution changes the date
Saving more each month brings your Coast FIRE age forward — see exactly how much.
| Monthly contribution | Coast FIRE age | From now |
|---|
What is Coast FIRE?
Coast FIRE is the point at which the money you have already invested is large enough to grow into a full retirement fund on its own, with no further contributions. You are not retired and you have not stopped working. You have stopped saving for retirement, because retirement is already funded — it just has not arrived yet.
The distinction matters because Coast FIRE arrives far earlier than full financial independence. Full FIRE requires the entire portfolio today. Coast FIRE requires only enough that compounding can finish the job before you retire. The younger you are, the smaller that fraction is, because you are handing the market more years to do the work.
What it buys is optionality: the freedom to take the job you would prefer over the job that pays most, to go part-time, to start something risky, or simply to stop worrying about your savings rate — without touching a penny of what is already invested.
How the Coast FIRE number is calculated
Three steps, and no step is hidden in this calculator — you can check every one of them against the panel above.
- Find your FIRE number. Annual retirement spending divided by your safe withdrawal rate. At $40,000 a year and a 4% withdrawal rate, that is $40,000 ÷ 0.04 = $1,000,000, expressed in today's money.
- Convert the nominal return into a real one. A 7% return against 3% inflation is not 4%. It is (1.07 ÷ 1.03) − 1 = 3.88%. Using 4% here instead would understate the number you need, and this is the single most common error in Coast FIRE arithmetic.
- Discount the FIRE number back to today. Divide it by (1 + real return) raised to the number of years until retirement. Over 30 years at 3.88%: $1,000,000 ÷ 1.038830 = $318,862.
That last figure is your Coast FIRE number. Hit it, and contributions become optional rather than necessary.
What your return assumption actually does to the number
Most Coast FIRE calculators hand you one number and move on. That number is far more fragile than it looks, and you deserve to see how fragile before you make a decision on it.
Here is the same person — 30 years old, retiring at 60, spending $40,000 a year, 4% withdrawal rate, 3% inflation — with nothing changed except the assumed nominal return:
| Nominal return | Real return | Coast FIRE number today |
|---|---|---|
| 5% | 1.9% | $561,614 |
| 6% | 2.9% | $422,611 |
| 7% | 3.9% | $318,862 |
| 8% | 4.9% | $241,215 |
| 9% | 5.8% | $182,946 |
Read that again: a four-point swing in one assumption moves the answer from $183,000 to $562,000. The optimistic figure is roughly three times smaller than the cautious one. Nobody knows which row the next thirty years will resemble.
The honest conclusion is not that the calculation is useless — it is that a Coast FIRE number is a range, not a threshold. If you are close to the number under an optimistic assumption and far from it under a cautious one, you have not reached Coast FIRE. You have reached the beginning of an argument with yourself.
Coast FIRE vs the other FIRE variants
| Variant | Are you still working? | What it means |
|---|---|---|
| Coast FIRE | Yes, full or part-time | Retirement is fully funded by compounding; you only need to cover today's costs |
| Barista FIRE | Yes, part-time | Part-time income plus portfolio withdrawals cover your costs, often chosen for healthcare access |
| Full FIRE | No | The portfolio covers everything today |
| Lean FIRE | No | Full FIRE on a deliberately small spending target |
| Fat FIRE | No | Full FIRE with a comfortable, unconstrained spending target |
Coast FIRE and Barista FIRE get confused constantly, and the difference is simple: a coaster's portfolio is untouched and still growing, while a Barista FIRE portfolio is already being drawn on. The side-by-side is in Coast FIRE vs Barista FIRE, and the two extremes are compared in Lean FIRE vs Fat FIRE.
The Coast FIRE formula
- Spending — your annual retirement cost, in today's dollars
- SWR — safe withdrawal rate, commonly 4% (0.04)
- r — the real return: (1 + nominal) ÷ (1 + inflation) − 1
- t — years between now and your target retirement age
Because everything is expressed in today's dollars, the answer means what you think it means: it is what you would need in your account this year, not a future figure inflated beyond recognition.
See the formula with your own numbers
These update live from the calculator inputs above. The calculator then simulates your monthly contributions to find the exact month your portfolio first crosses the line.
Example: what the number looks like at different ages
Same plan throughout — retire at 60, spend $40,000 a year, 4% withdrawal rate, 7% return against 3% inflation, so a $1,000,000 FIRE number. Only the starting age changes.
| Your age today | Years of compounding left | Coast FIRE number today | Share of the full FIRE number |
|---|---|---|---|
| 25 | 35 | $263,555 | 26% |
| 30 | 30 | $318,862 | 32% |
| 35 | 25 | $385,777 | 39% |
| 40 | 20 | $466,733 | 47% |
| 45 | 15 | $564,679 | 56% |
This is the whole argument for starting early, stated in one column. A 25-year-old needs about a quarter of the final number; a 45-year-old needs more than half. The money is identical — what differs is how many years it gets to work.
Working the default scenario through: a 30-year-old with $50,000 invested and $1,500 a month going in crosses the Coast FIRE line at roughly age 52. From then on, contributions are optional.
What Coast FIRE asks you to accept
Coast FIRE lives or dies on the return assumption, because the entire thesis is that growth alone covers the remaining decades. You are betting on multi-decade market growth with no further contributions to smooth the ride, and a poor decade early in the coast leaves less time to recover precisely because you deliberately stopped adding.
Which is why few people treat it as a hard switch:
- Partial coast — cut contributions substantially rather than to zero, keeping a margin against poor returns.
- Coast to a change — hit the number, then move to work that pays less but suits you better.
- Recheck annually — treat the number as a moving target and top up if markets disappoint. Coasting is a decision you get to remake every year.
Frequently asked questions
What is a Coast FIRE number?
It is the amount you would need invested today so that, with no further contributions, compounding alone grows it into your full FIRE number by your target retirement age. It is calculated by taking your FIRE number (annual spending divided by your withdrawal rate) and discounting it back to today at your real return. For a 30-year-old retiring at 60 on $40,000 a year, that is about $318,862 against a $1,000,000 FIRE number.
How do you calculate Coast FIRE?
Three steps. First, FIRE number = annual spending ÷ safe withdrawal rate. Second, real return = (1 + nominal return) ÷ (1 + inflation) − 1 — not nominal minus inflation, which is a close but consistently wrong shortcut. Third, Coast number = FIRE number ÷ (1 + real return)years to retirement. The calculator above shows all three with your figures.
Does Coast FIRE mean you can stop working?
No. It means you can stop saving for retirement. You still need income to cover today's living costs — rent, food, insurance. What changes is that none of that income has to go into the retirement account any more, which is what makes a lower-paid or part-time job viable.
What return should I use for Coast FIRE?
There is no correct answer, and that is the point. A stock-heavy portfolio is often modelled at around 7% nominal, but as the table above shows, moving between 5% and 9% swings the required number from $562,000 to $183,000. Run your number at a cautious rate as well as an optimistic one and treat the gap as your margin of error.
What if markets underperform after I stop contributing?
Then you arrive with less than planned and must work longer, spend less, or resume contributions. This is the central risk of coasting and it has no clever solution. It is why many people coast partially rather than fully, and why rechecking the number every year matters more than hitting it once.
Does Coast FIRE include a paid-off house?
Only if you say so. If you will still have a mortgage in retirement, your annual spending figure must include it, which raises the FIRE number and pushes the coast point later. Most people model the target as post-mortgage spending, so check which one you entered.
Is Coast FIRE realistic starting in my forties?
Harder, but not impossible — there are simply fewer compounding years, so the required balance sits much closer to the full number. At 45 you need about 56% of your FIRE number versus 26% at 25. The calculation is identical; the answer is just less flattering, which is exactly why it is worth running.
Method & sources
- Calculation: FIRE number = annual spending ÷ safe withdrawal rate; Coast number = FIRE ÷ (1 + real return)years; contributions simulated monthly in real dollars. Verified against an independent test suite.
- The 4% safe withdrawal rate comes from the widely cited Trinity study; it is a planning guide, not a guarantee.
- Reviewed: · Assumptions reviewed quarterly.
Educational estimate, not financial advice. Investment returns vary and can be negative.
Run your own numbers
Your Coast FIRE number depends entirely on your age, your target and the return you are willing to assume. Put yours in and see the number — and the year you could stop saving.
Back to the calculator ↑