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Coast FIRE calculator

How much you need invested today to stop saving and still retire on time.

To spend $40,000 a year from 65 at a 4% withdrawal rate you need $1,000,000. At 35, growing 5% a year after inflation, $231,377 gets there on its own: that is your coast FIRE number.

Age 46.8

Coast FIRE number today

$231,377

Grows to your FIRE number of $1,000,000 by age 65 with no more saving, at 5% a year after inflation.

You have 43% of it. Saving $15,000 a year you get there in 11.8 years.

Solid line: your portfolio, saving until the green plate and then growing on its own. Dashed line: the coast FIRE number at each age.

Age now	Years to 65	Coast FIRE number
25	40	$142,046
30	35	$181,290
35	30	$231,377
40	25	$295,303
45	20	$376,889
50	15	$481,017
55	10	$613,913
60	5	$783,526

Chart data

Age	Your portfolio	Coast FIRE number
35	$100,000	$231,377
40	$210,513	$295,303
45	$351,558	$376,889
50	$481,017	$481,017
55	$613,913	$613,913
60	$783,526	$783,526
65	$1,000,000	$1,000,000

How coast FIRE is calculated

Coast FIRE means having enough invested that, with no more saving, growth alone takes it to your FIRE number by your retirement age. Your earnings then only need to cover your spending until then.

Coast FIRE number = FIRE number ÷ (1 + r)^{years to retirement}

With $40,000 a year at a 4% withdrawal rate the FIRE number is $1,000,000. At 35, with 30 years to go and 5% a year after inflation, $1,000,000 ÷ 1.05³⁰ = $231,377.

The age you reach it is when your growing portfolio meets the rising coast number. With $100,000 invested and $15,000 saved a year, that takes 11.8 years: age 46.8.

The return you assume matters most

Because the money grows for decades, a small change in the return moves the answer a lot. The coast FIRE number at 35 for the same $1,000,000 goal at 65:

Real return a year	Coast FIRE number at 35
3%	$411,987
4%	$308,319
5%	$231,377
6%	$174,110
7%	$131,367

Entering a 7% return before inflation as if it were real gives $131,367. With 3% inflation the real return is 3.88%, and the coast number is $318,862: $187,495 more. If you choose "Before inflation", the calculator makes that conversion for you.

Coast FIRE assumes the portfolio is left alone for 30 years and grows at the same rate every year. Real returns vary, and a few bad years can push the date back. These are illustrations, not forecasts; see the disclaimer.

What coast FIRE leaves out

You still need income for your spending until retirement age: coast FIRE only means you can stop adding to the portfolio.
Taxes and investment fees are not included, and neither are Social Security or pensions, which would lower the FIRE number.
Withdrawing from the portfolio before retirement age, even once, breaks the calculation.
The FIRE number uses the same withdrawal rate as the FIRE calculator; for an early or long retirement, test a lower rate.

Questions people ask

What does it mean to coast FIRE?

It means you have enough invested that, without adding more, growth alone will reach your FIRE number by retirement age. In the example above, $231,377 at 35 grows to $1,000,000 by 65 at 5% a year after inflation, while work still pays your living costs until then.

What is a good coast FIRE age?

Coast FIRE has no standard age: it is whenever your portfolio reaches the coast number for your age. In the example, starting with $100,000 and saving $15,000 a year, that happens at 46.8. The coast FIRE guide has the age for other starting points and saving levels.

FIRE calculator: your FIRE number and the age you reach it for lean, regular and fat FIRE. Methodology: every formula and default, and how the calculators are tested.

Sources

William P. Bengen, "Determining Withdrawal Rates Using Historical Data", Journal of Financial Planning, October 1994, the origin of the 4% withdrawal rate.
U.S. Bureau of Labor Statistics, Consumer Price Index, for US inflation history.

Last reviewed by Asier Fernández, editor, on October 18, 2026. Educational information only, not financial advice. How we calculate