FIRE Number: How to Calculate It (With Examples)

The formula

FIRE number = annual spending ÷ withdrawal rate

Annual spending is what you expect to spend in a year once you stop working, in today's dollars, including taxes and health insurance. The withdrawal rate is the share of the portfolio you take out in the first year; after that the withdrawal rises with inflation, as the 4% rule describes. At 4% the FIRE number is 25 times your spending, at 3.5% about 28.6 times and at 3% about 33.3 times.

Three worked examples

$30,000 a year at 4%

$30,000 ÷ 0.04 = $750,000.

$60,000 a year at 3.5%

$60,000 ÷ 0.035 = $1,714,286. The more cautious rate adds $214,286 compared with 4% ($1,500,000).

$100,000 a year at 3%

$100,000 ÷ 0.03 = $3,333,333.

FIRE number by spending and withdrawal rate

Spending a year	3% withdrawal	3.5% withdrawal	4% withdrawal
$30,000	$1,000,000	$857,143	$750,000
$40,000	$1,333,333	$1,142,857	$1,000,000
$50,000	$1,666,667	$1,428,571	$1,250,000
$60,000	$2,000,000	$1,714,286	$1,500,000
$80,000	$2,666,667	$2,285,714	$2,000,000
$100,000	$3,333,333	$2,857,143	$2,500,000
$120,000	$4,000,000	$3,428,571	$3,000,000

FIRE number by annual spending. Each line is a withdrawal rate; the plate marks $40,000 a year at 4%.

Which rate to use depends mostly on how long the money has to last. Morningstar's latest estimates are 3.9% for a 30-year retirement and 2.9% for 50 years; the details are in the 4% rule explained.

Lower it with other income

Only the spending your portfolio has to pay counts. Subtract income that does not come from it, such as a pension, rent from a property or Social Security:

Adjusted FIRE number = (annual spending − other income) ÷ withdrawal rate

Other income a year	Portfolio pays	FIRE number at 4%
$0	$40,000	$1,000,000
$10,000	$30,000	$750,000
$20,000	$20,000	$500,000
$30,000	$10,000	$250,000

When the income starts later

Social Security usually starts years after an early retiree stops working. Retirement benefits can begin at 62 at the earliest, reduced, and full benefits start at 67 for anyone born in 1960 or later. A simple way to plan for the gap is a bridge: set aside the missing $20,000 a year until benefits start, and size the rest of the portfolio for the lower spending.

Stop working at	Years until 67	Bridge at $20,000 a year	Portfolio for $20,000 at 4%	Total
40	27	$540,000	$500,000	$1,040,000
45	22	$440,000	$500,000	$940,000
50	17	$340,000	$500,000	$840,000
55	12	$240,000	$500,000	$740,000

The bridge assumes no growth, which is cautious. Retiring at 40, the bridge alone is $540,000, so the total ends up close to the plain $1,000,000. The earlier you stop working, the less Social Security lowers what you need on your first day of retirement. Use the benefit estimate on your own Social Security statement; $20,000 here is only an example. The Early Retirement Now series looks at how later income like this changes the safe withdrawal rate.

The FIRE number is in today's dollars

The FIRE number is in today's dollars. Prices rise, so the same life costs more later: with 3% inflation, $1,000,000 of today's money is $1,742,152 in 18.8 years, when the example household in the FIRE calculator gets there. That is why the calculator grows your savings at a return after inflation, comparing today's dollars with today's dollars.

These figures are illustrations worked out from stated assumptions, not forecasts. Real returns vary from year to year, and taxes, fees and the order of good and bad years change the outcome. See the disclaimer.

Common mistakes

Using your take-home pay. The number depends on what you spend, so a household that earns $90,000 and spends $40,000 needs $1,000,000; 25 times its pay would be $2,250,000.
Forgetting irregular costs. A $30,000 car every ten years adds $3,000 a year to spending and $75,000 to the FIRE number at 4%.
Counting the home you live in. It pays for groceries only if you sell it or rent it out.

Questions people ask

What is our FIRE number as a couple?

Use the same formula with the household's combined spending: a couple that spends $60,000 a year needs $1,500,000 at 4%. Count each partner's Social Security or pension separately, because they may start at different ages.

How long will $750,000 last in retirement at 62?

It depends on how much you take out and what the portfolio earns. With a steady 3% return after inflation and withdrawals at the start of each year, taking 4% ($30,000 a year) lasts 44.1 years, to about age 106; taking 5% ($37,500) lasts 29.6 years, to about age 91; taking 6% ($45,000) lasts 22.5 years, to about age 84. Social Security can also start at 62, reduced: for anyone born in 1960 or later, benefits claimed at 62 are 30% lower than at 67.

Can I retire at 40 with $2 million?

That depends on what you spend. Morningstar's latest starting rates are 3.3% for a 40-year retirement and 2.9% for 50 years, which on $2,000,000 means a first-year withdrawal of $58,000 to $66,000. At 4% it would be $80,000. Health insurance until Medicare at 65 belongs in that spending.

Calculate yours

Enter your spending in the FIRE calculator to see your FIRE number and the age you reach it. What is FIRE explains the idea, and lean vs fat vs coast vs barista FIRE compares the versions.

Sources

William P. Bengen, "Determining Withdrawal Rates Using Historical Data", Journal of Financial Planning, October 1994.
Philip L. Cooley, Carl M. Hubbard and Daniel T. Walz, "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable", AAII Journal, February 1998 (the Trinity study).
Amy C. Arnott, "How Much Can You Safely Withdraw If You Retire Early?", Morningstar, September 15, 2026 (data as of September 30, 2025).
Karsten Jeske, The Safe Withdrawal Rate Series, Early Retirement Now (blog series, 2016 onward).
Social Security Administration, Starting Your Retirement Benefits Early.

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

How to calculate your FIRE number