FIRE Number by Expenses

The short answer

Take your expected annual expenses in retirement and multiply by 25. That is your FIRE number under the 4 percent rule. Spend $40,000 a year and the target is about $1,000,000; spend $50,000 and it is $1,250,000; spend $80,000 and it is $2,000,000. The number is driven entirely by your spending, not your income, which is why lowering expenses lowers the finish line.

FIRE number by annual expenses

Using the 25x rule (a 4 percent withdrawal rate), here is the target for a range of spending levels:

Every $10,000 of annual spending adds $250,000 to the target. That direct link is why cutting recurring costs is so powerful for anyone chasing FIRE — it shrinks the number twice over, by needing less and letting you save more.

That doubling is worth putting numbers on, because it is the strongest lever in a FIRE plan. Cutting $5,000 from a $50,000 budget pulls the target down from $1,250,000 to $1,125,000, and the same $5,000 becomes an extra annual contribution. For someone already saving $25,000 a year at 5 percent after inflation, starting from zero, the lower target on its own would save about 1.5 years; both effects together bring the finish line in by about four years — 21.6 years instead of 25.7. A $5,000 raise, by contrast, moves only the savings side of that pair.

Expenses × withdrawal rate

The 25× rule is an assumption, not a fact. The withdrawal rate you plan around sets the multiple, and the multiple sets the target. This matrix crosses six spending levels with the three rates most early-retirement plans are built on:

Read across any row and the withdrawal assumption swings the target by 25.4 percent of the 4 percent figure — and by the same 25.4 percent on every row, because the whole calculation is proportional. Planning at 3.5 percent instead of 4 percent adds exactly 14.3 percent to your number; planning at 4.5 percent takes exactly 11.1 percent off it, whether you spend $30,000 a year or $100,000. The spending level decides how big the number is. The rate decides how wrong it can be.

What the rate choice costs in time

The dollar gaps in the last column look enormous, but the question that actually decides a plan is how many extra years of saving they represent. Take someone with $50,000 of annual expenses who saves $25,000 a year, earns 5 percent a year after inflation and starts from zero:

A $317,460 spread in the target compresses into less than four years of working life, because the portfolio is growing fastest at the end — the last few years of compounding cover most of the difference. That is the real trade behind the rate you pick: about two extra years of saving in exchange for a thinner withdrawal, or two years earlier in exchange for a thicker one. No rate in the table is safe in any guaranteed sense; safe withdrawal rate explained covers what the underlying research does and does not support, and what FIRE is covers how the rate fits the wider strategy.

From monthly expenses

If you budget monthly, multiply your monthly spending by 12 to get the annual figure, then by 25. Or just multiply monthly expenses by 300:

The shortcut works because 12 months times 25 years equals 300. A $3,000-a-month lifestyle needs about $900,000 invested to sustain it under the 4 percent rule.

Lean, regular, and fat FIRE

The same math produces very different numbers depending on the lifestyle you are funding:

• Lean FIRE — spending under roughly $40,000 a year, so a target under about $1,000,000. It relies on a frugal, low-cost lifestyle.
• Regular FIRE — a typical middle-class budget of $40,000 to $80,000 a year, needing about $1,000,000 to $2,000,000.
• Fat FIRE — a comfortable or high-spending lifestyle of $100,000 a year or more, requiring $2,500,000 and up.

None is more “correct” than another — they simply reflect different spending, and the 25x rule scales cleanly across all of them.

The math behind it

The FIRE number comes straight from your withdrawal rate:

At a 4 percent withdrawal rate, dividing by 0.04 is the same as multiplying by 25 — hence the 25x rule. Choose a 3.5 percent rate and you divide by 0.035, or multiply by about 28.6. The withdrawal rate is really an assumption about how much a diversified portfolio can safely pay out each year without running dry over a long retirement. To see how contributions and compounding get you to the target, try how much $250 a month grows in 30 years.

Your number is in today's dollars

Every figure above is expressed in today's purchasing power. That is the right way to set a target, but it creates a trap: a projection of what a portfolio will be worth in twenty years is normally quoted in future dollars, and comparing that to a target in today's dollars makes you look closer to the finish line than you are.

A $50,000 lifestyle does not stay a $50,000 lifestyle. At 3 percent inflation:

All four rows buy the same standard of living. There are two internally consistent ways to handle that, and mixing them is the most common arithmetic mistake in early-retirement planning:

• Plan in today's dollars. Keep the target at 25 times today's expenses and project the portfolio with a real return — the 5 percent after inflation used in the tables above, not a nominal 7 or 8 percent.
• Plan in future dollars. Inflate the expenses and the target, then project with a nominal return. This produces the same answer in years, with bigger numbers on both sides.

The 3 percent used here is a round number chosen for legible arithmetic, not a forecast. To work from measured inflation instead, the U.S. Bureau of Labor Statistics publishes the CPI-U series. The inflation-adjusted future value calculator reports a nominal and a real result side by side.

What the tables leave out

The multiple is the easy part. The reason two people with identical spending can need very different portfolios is everything that sits outside the division:

• Taxes are not modeled. The tables divide spending by a withdrawal rate and say nothing about what you owe on the withdrawal. Money leaving a pre-tax account is taxable income, so a $50,000 lifestyle funded that way needs more than $50,000 withdrawn; Roth and taxable accounts are taxed differently or already taxed. Put the tax bill inside your expense figure, or the target is too low before you start.
• Health coverage before Medicare. For a US early retiree, insuring the years before Medicare coverage begins is often the largest new line in the budget, and the least predictable one — what it costs can depend on your income, which depends on how you draw the portfolio down.
• Large irregular expenses. A roof, a car, dental work and a family emergency never appear in an average monthly budget, and arrive anyway. Either raise the annual expense figure to carry a share of them or hold a separate reserve, but do not leave them out of both.
• Income you have not counted. Social Security, a pension, part-time work or rental income all shrink the portfolio you need, because the portfolio only has to cover the gap that is left. None of these tables assume any of it.
• A rigid withdrawal. The multiples come from a rule that withdraws a fixed, inflation-adjusted amount every year regardless of what markets did. Real retirees cut back after a bad year, which is precisely why the rule is a conservative planning device and a poor description of behaviour.
• Sequence of returns. The average return is not the main risk; the order the returns arrive in is. A weak first decade can drain a portfolio that a strong first decade would have grown, at exactly the same average.

None of that makes the 25× rule useless. It makes it a starting point — a number you can work out in one line, then adjust for the parts of your situation the line knows nothing about. Treat the result as a planning scenario to revisit as your real expenses become clearer, not as a threshold that guarantees anything.

Assumptions behind these figures

• A fixed withdrawal rate. The tables assume you withdraw a constant percentage (4 percent unless stated) of the starting portfolio, adjusted for inflation.
• Expenses stay roughly constant in real terms. The number reflects today's spending; large lifestyle changes shift the target.
• Taxes and health care are part of expenses. Use total real spending in retirement, not pre-tax income — see what the tables leave out.
• A guideline, not a guarantee. The 4 percent rule is based on historical data; a poor sequence of early returns can still require flexibility.

How these figures were checked

• Targets. Every portfolio figure is annual expenses divided by the withdrawal rate, computed at full precision and rounded to the nearest dollar for display only. The multiples are 1 ÷ 0.035 = 28.5714, 1 ÷ 0.04 = 25 and 1 ÷ 0.045 = 22.2222.
• Years of saving. Solved from the ordinary annuity relationship n = ln(1 + FV × r ÷ PMT) ÷ ln(1 + r), using annual contributions, a 5 percent real return and a zero starting balance, then rounded to one decimal.
• Inflated costs. Compounded as $50,000 × 1.03ⁿ, with each matching target at 25 times the inflated expense figure.
• Sources. The arithmetic here needs none — it is division and compounding, and every table was recomputed independently before publication. The single external pointer is the BLS CPI-U series for measured inflation. The research behind the 3.5 to 4.5 percent range is cited on the safe withdrawal rate page.

Frequently asked questions

The bottom line

Your FIRE number is simpler than it sounds: annual expenses times 25, or divided by your chosen withdrawal rate. Spend $40,000 a year and you need about $1,000,000; spend more and the target rises in direct proportion. Because it tracks spending rather than income, the fastest way to move the finish line closer is to know — and manage — your real expenses.

Turn your own numbers into a target and a timeline with the FIRE calculator, and read what is FIRE for the full strategy.