If you've ever daydreamed about walking away from a job you don't love, you've probably run into the same wall: the number feels enormous. A million dollars. Two million. Whatever it is, it sits far enough away that the whole idea looks like a 30-year project.
Coast FIRE changes the math.
The idea is simple: you only need to save hard until your nest egg reaches a point where compound growth does the rest of the work. After that, you can stop contributing entirely — switch to a lower-paying job, work part-time, take a few years off — and your existing balance will still grow into enough to retire on.
The catch is that the magic number moves depending on how old you are right now. At 25, you have four decades of compounding ahead of you. At 50, you have fifteen. Same target, completely different starting line.
So what does the number actually look like at each age? Let's run it.
How the math works (the short version)
Two rules drive everything here:
- The 25x rule. A common retirement benchmark says you need about 25 times your annual spending invested to retire safely. It comes from the 4% withdrawal rate: if you pull 4% of your portfolio out in year one and adjust for inflation after that, the historical odds of the money lasting 30 years are very high. The number traces back to William Bengen's 1994 research and the 1998 Trinity Study, which tested withdrawal rates against U.S. market returns going back to 1926 (Cooley, Hubbard & Walz, AAII Journal).
- Compound growth. Money you already have grows on its own. At a 7% average annual return, it roughly doubles every decade.
Put them together and your Coast FIRE number at any age is:
Coast FIRE number = (25 × annual spending) ÷ 1.07^(years until retirement)
The assumptions baked into that formula matter, so let's name them up front:
- 7% average annual return, with dividends reinvested. The S&P 500 has averaged roughly 10% a year nominally over the long run, but 7% is a more conservative figure that accounts for inflation and gives you a cushion against optimistic projections (Fidelity).
- Retirement at 65.
- A portfolio that stays invested in the market through the whole period — no cashing out during a crash.
These are the same defaults our Coast FIRE calculator uses, and you can change every one of them.
Coast FIRE numbers by age
Here's what it takes at each age to "coast" into a standard retirement at 65, depending on how much you spend per year. The numbers below are the invested balance you'd need today.
| Age | Spending $50k | Spending $60k | Spending $75k | Spending $100k |
|---|---|---|---|---|
| 25 | $83,475 | $100,171 | $125,213 | $166,951 |
| 27 | $95,571 | $114,685 | $143,357 | $191,142 |
| 30 | $117,079 | $140,494 | $175,618 | $234,157 |
| 32 | $134,043 | $160,852 | $201,065 | $268,087 |
| 35 | $164,209 | $197,051 | $246,313 | $328,418 |
| 37 | $188,003 | $225,603 | $282,004 | $376,006 |
| 40 | $230,311 | $276,374 | $345,467 | $460,623 |
| 42 | $263,684 | $316,420 | $395,525 | $527,367 |
| 45 | $323,024 | $387,629 | $484,536 | $646,048 |
| 47 | $369,830 | $443,796 | $554,745 | $739,660 |
| 50 | $453,058 | $543,669 | $679,586 | $906,115 |
Read across a row and you'll notice the whole thing is just a multiple of spending. A 35-year-old needs about 3.3 years of expenses in the bank. A 50-year-old needs about 9.1.
The table that actually matters: multiples of spending
If your spending doesn't match one of the columns above, the multiples table is the one to bookmark. Take your annual spending and multiply it by the figure next to your age.
| Age | Years to 65 | Multiple of annual spending |
|---|---|---|
| 25 | 40 | 1.67x |
| 27 | 38 | 1.91x |
| 30 | 35 | 2.34x |
| 32 | 33 | 2.68x |
| 35 | 30 | 3.28x |
| 37 | 28 | 3.76x |
| 40 | 25 | 4.61x |
| 42 | 23 | 5.27x |
| 45 | 20 | 6.46x |
| 47 | 18 | 7.40x |
| 50 | 15 | 9.06x |
This is the part people find hard to believe. A 30-year-old who spends $60,000 a year doesn't need anywhere near $1.5 million. They need roughly $140,000 — and then they can let it ride for 35 years.
That's not because the target shrank. The full number at retirement is still $1.5 million. It's because $140,000, compounding at 7% for 35 years, becomes $1.5 million without another dollar going in.
What real people spend
"Annual spending" sounds like a number you should know, and most of us don't, exactly. Here's a reference point from actual government data.
According to the Bureau of Labor Statistics' Consumer Expenditure Survey, the average American household's annual spending in 2024 broke down like this by the age of the reference person (BLS Consumer Expenditure Survey, via FRED):
| Age of reference person | Average annual spending, 2024 |
|---|---|
| 25–34 | $74,475 |
| 35–44 | $91,229 |
| 45–54 | $100,327 |
| 55–64 | $84,946 |
| 65+ | $61,432 |
A few honest caveats. These are averages, not recommendations — they include things you might not have (kids, a mortgage) and exclude things you might (elder care, student loans). They also include pension and Social Security contributions deducted from paychecks, which mostly disappear once you're coasting and living off a lighter income. And the BLS "consumer unit" isn't always exactly a household.
Use them as a starting guess, then replace the number with your own. Pull three months of bank and credit card statements, annualize the total, and you've got the figure that actually belongs in the formula.
A real example
Say you're 30, married, and your household spends about $75,000 a year.
- Full retirement target: 25 × $75,000 = $1,875,000
- Coast FIRE number at 30: that target divided by 1.07 to the 35th power = about $176,000
If you hit $176,000 invested and then never contributed another cent, a 7% return gets you to roughly $1.9 million by 65. You could take a job that covers your bills but pays less, go part-time, start something of your own — the retirement math is already handled.
What you can't do at that point is stop earning. Coast FIRE isn't full FIRE. You still need to cover your living costs until retirement; it's the retirement savings burden that disappears. If you want the version where you never work again, that's regular FIRE, and the number is the full 25x today. If a little part-time work sounds fine to you, Barista FIRE sits in between and might be the closer fit.
What if the assumptions change?
Seventy percent of the arguments about FIRE numbers are really arguments about assumptions, so let's show how much they swing things. Here's the balance you'd need today on $60,000 of spending at three different return rates:
| Age | At 5% | At 6% | At 7% |
|---|---|---|---|
| 25 | $213,069 | $145,833 | $100,171 |
| 30 | $271,935 | $195,158 | $140,494 |
| 35 | $347,066 | $261,165 | $197,051 |
| 40 | $442,954 | $349,498 | $276,374 |
| 45 | $565,334 | $467,707 | $387,629 |
| 50 | $721,526 | $625,898 | $543,669 |
One percentage point of assumed return changes the 30-year-old's number by more than $50,000. That's why planning on 10% — the S&P's long-run nominal average — is risky. The market can return 10% over a century while your particular 30-year window includes a miserable decade at the start. A lower assumed return means a bigger balance today and a plan that survives more bad luck. If you hit 7% anyway, you just end up ahead.
The retirement age you pick matters too. Planning to stop at 62 instead of 67 gives the money less time to grow and costs you a higher number today; delaying to 67 lowers it. Here's the same $60,000 spender at three different finish lines, with a 7% return:
| Age | Retire at 62 | Retire at 65 | Retire at 67 |
|---|---|---|---|
| 25 | $122,713 | $100,171 | $87,493 |
| 30 | $172,112 | $140,494 | $122,713 |
| 35 | $241,396 | $197,051 | $172,112 |
| 40 | $338,570 | $276,374 | $241,396 |
| 45 | $474,862 | $387,629 | $338,570 |
| 50 | $666,018 | $543,669 | $474,862 |
The honest fine print
These numbers are planning tools, not promises. A few things worth keeping in view:
- Sequence-of-returns risk is real. The model assumes a smooth 7%. Actual returns arrive in lumps, and a crash in the first years after you stop saving does outsized damage, because it hits the balance before it has grown. If you're coasting through a downturn, a year or two of modest contributions is the cheapest insurance there is.
- Inflation is always moving. U.S. inflation has averaged about 3% a year since 1926 (Minneapolis Fed), which is why using a conservative nominal return matters. Your future $1.9 million won't spend like $1.9 million today — but a balance that compounds in nominal dollars and spending that roughly tracks inflation keeps the relationship roughly stable. We dig into this in the piece on why we use 7% average returns.
- Health care doesn't take care of itself. Once you're working less, you're buying your own health insurance until Medicare kicks in. For most people this is the single biggest expense the tables above don't show, so price it before you hand in notice.
- Fees and taxes come out the top. The 7% is a gross figure. Low-cost index funds keep fees near zero; holding them in tax-advantaged accounts keeps the tax bill down too.
Find your own number
The whole point of Coast FIRE is that the finish line is closer than the scary 25x number makes it sound — especially if you're young. A 25-year-old needs less than two years of expenses invested to be on track. A 40-year-old needs under five.
If you haven't seen your own figure yet, run it through the Coast FIRE calculator — enter your current balance, spending, and expected return, and it'll show you the age you're on track for and how far you are from your coast line. Lean FIRE vs Fat FIRE is a good next stop if you're not sure which lifestyle the number should be built around.
Then go save. The earlier the number gets hit, the earlier compounding starts working for you instead of against you.
Sources
- The 4% rule and 25x benchmark. Based on William Bengen's 1994 research and the 1998 Trinity Study (Cooley, Hubbard & Walz, AAII Journal, February 1998), which tested withdrawal rates against U.S. stock and bond returns back to 1926. Reprint: Sustainable Withdrawal Rates in Retirement (RBC Wealth Management).
- Average annual spending by age, 2024. U.S. Bureau of Labor Statistics, Consumer Expenditure Survey, via FRED: 25–34 ($74,475), 35–44 ($91,229), 45–54 ($100,327), 55–64 ($84,946), 65+ ($61,432).
- S&P 500 long-run average return (~10% nominally). Fidelity, "What is the S&P 500?"
- Historical U.S. inflation (~3% average since 1926). Federal Reserve Bank of Minneapolis, Consumer Price Index 1913–present
Figures are as of September 2026 and are calculated using a 7% assumed annual return, retirement at 65, and dividends reinvested. This article is general information, not financial advice; market returns are not guaranteed and your actual results will differ. Please consult a qualified professional for your own planning.