FIRE Number Calculator

Calculate how much you need invested to retire early, using the 4% rule or any withdrawal rate you choose.

Assumptions reviewed

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%
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$
Your FIRE number
$1,500,000

At 4%, every $1,000 you cut from yearly spending lowers your FIRE number by $25,000.

FIRE number by withdrawal rate
$0$500K$1M$1.5M$2M3% — FIRE number: $2,000,0003%3.25% — FIRE number: $1,846,1543.25%3.5% — FIRE number: $1,714,2863.5%3.75% — FIRE number: $1,600,0003.75%4% — FIRE number: $1,500,0004%4.5% — FIRE number: $1,333,3334.5%5% — FIRE number: $1,200,0005%
Times your yearly gap
25 ×
Spending your portfolio must cover
$60,000
Monthly withdrawal
$5,000
Progress so far
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Still to save
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Show the working
  1. FIRE number = $60,000 ÷ 4% = $60,000 × 25 = $1,500,000

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Formula

FIRE number = (annual spending − guaranteed income) ÷ withdrawal rate4% rule: FIRE number = 25 × annual spending

How it works

Your FIRE number is the size of the investment portfolio that can pay for your life without a job. It comes from a single division: the yearly spending your portfolio needs to cover, divided by a withdrawal rate you are comfortable with.

The 4% rule is the most famous version. Dividing by 4% is the same as multiplying by 25, so someone who spends $60,000 a year needs $1.5 million. Lower withdrawal rates mean a bigger number but more safety: at 3.5%, that same retiree needs about $1.71 million.

If you will have income you can rely on from day one — a pension, a paid-off rental, an annuity — subtract it first. Only the gap needs to come from your investments, which can shrink the target dramatically.

Where the 4% rule comes from

In 1994 the financial planner William Bengen tested withdrawal strategies against US market history and found that starting at about 4% of a stock-and-bond portfolio, then raising the amount with inflation, never ran out of money within 30 years. The 1998 "Trinity study" reached a similar conclusion.

Early retirees face longer horizons. Over 40–60 years, a 4% rate has failed in some historical periods, so many FIRE planners use 3.25–3.75% or keep the flexibility to trim spending after a market crash.

How to find your retirement spending

Start from what you actually spend today, using a year of bank and card statements. Then adjust: remove costs that end at retirement (commuting, retirement contributions, a mortgage you will have paid off) and add new ones such as private health insurance and more travel.

Frequently asked questions

Is my FIRE number in today's dollars?

Yes. If you spend $60,000 today, a $1.5 million FIRE number means $1.5 million of today's purchasing power. In 15 years at 3% inflation the nominal figure would be about $2.3 million.

What is the 25x rule?

It is the 4% rule turned around: 1 ÷ 4% = 25, so you need 25 times your yearly spending. At 3.5% the multiple is about 28.6, and at 3% it is about 33.3.

Should I include Social Security?

Only if you will retire close to when you can claim it. Early retirees usually have a gap of 20+ years before benefits start, so they leave it out of the FIRE number and treat it as a later safety margin.

Does my FIRE number include taxes?

Only if your spending figure does. Withdrawals from traditional 401(k)s and IRAs are taxed as income, so add your expected tax to your spending, or use the Fat FIRE calculator, which grosses spending up by a tax rate.

Sources

  • Bengen, W. P. (1994). "Determining Withdrawal Rates Using Historical Data." Journal of Financial Planning.
  • Cooley, Hubbard & Walz (1998). "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable." AAII Journal (the "Trinity study").
  • Early Retirement Now — Safe Withdrawal Rate Series
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