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FIRE Calculator

Find your FIRE number — the portfolio size needed to cover your annual expenses at a sustainable withdrawal rate — and see how many years of saving and investing it could take to get there.

Calculator

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The 4% figure popularized by the Trinity Study is a common reference point, not a rule
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How It Works

Your FIRE number is your annual expenses divided by your chosen withdrawal rate — mathematically the same as multiplying expenses by 25 at a 4% rate. This is a widely used planning shortcut, not a guarantee that a portfolio of that size will last indefinitely.

Years to FIRE is found by simulating your savings growing monthly at your expected return, with your contribution added each month, until the projected balance reaches your FIRE number.

Not included: Assumes a constant annual return with no volatility, which real markets never provide — sequence-of-returns risk (poor returns early in retirement) can meaningfully affect how long a portfolio actually lasts, even at a 'safe' withdrawal rate.

Formula

FIRE Number = Annual Expenses ÷ (Withdrawal Rate ÷ 100)
  • Annual Expenses — What you expect to spend per year in retirement
  • Withdrawal Rate — The percentage of the portfolio you plan to withdraw each year

Example

Example inputs: Age 30, $50,000 saved, $2,000/mo contribution, 7% expected return, $40,000/yr expenses, 4% withdrawal rate.

Result: FIRE number: $1,000,000. Years to reach it: about 17.7 — projected FIRE age of roughly 47.7.

Frequently Asked Questions

Is the 4% rule guaranteed to work?

No. It's a historically-derived guideline from U.S. market data (the Trinity Study), not a guarantee — actual safe withdrawal rates depend on the market conditions you retire into, how long retirement lasts, and your spending flexibility.

What's Coast FIRE?

A related concept where you stop contributing once your current savings alone are projected to grow to your FIRE number by a target age, purely through compounding — this calculator shows the standard model where contributions continue throughout.

Should I use a lower withdrawal rate to be safer?

Many people planning very long retirements (30+ years) use a more conservative rate like 3-3.5%, which raises the FIRE number and the time needed — you can test that directly by changing the withdrawal rate field.

This calculator provides estimates for informational purposes only and should not be considered financial, tax, or legal advice.