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FIRE Calculator

Estimate a FIRE number from today's annual expenses and a withdrawal-rate assumption, then project how long it may take for a growing portfolio to catch a moving, inflation-adjusted target. The FIRE target is a simplified planning estimate. It does not determine whether a portfolio will sustain withdrawals for any particular number of years.

Entered in today's dollars.

Illustrative planning assumption — not a recommendation or “safe” withdrawal rate.

Fixed nominal amount at the end of each month.

Effective annual return assumption — hypothetical, not guaranteed.

Effective annual price-change assumption used to move the FIRE target.

Optional. Used only to estimate FIRE age. Leave blank to omit.

Your results will appear here

Enter your assumptions and calculate to see the estimated result and supporting details.

How this calculator works

Enter today's annual expenses, withdrawal-rate assumption, current portfolio, monthly contribution, expected effective annual return, and inflation. Optionally enter current age to estimate FIRE age.

Each month expenses inflate, the FIRE target updates, the portfolio grows with an end-of-month contribution, and the calculator checks whether the portfolio meets the target. Search stops at 100 years.

Formula / methodology

currentFireNumber = expensesToday / withdrawalRate
expenses_m = expensesToday × (1 + monthlyInflation)^m
target_m = expenses_m / withdrawalRate
portfolio_m = portfolio_(m−1) × (1 + monthlyReturn) + contribution
  • Monthly return and inflation are equivalent effective monthly rates from the annual assumptions.
  • Contributions are fixed nominal end-of-month amounts.
  • If the current portfolio already meets the current FIRE number, time to FIRE is 0 months.

Worked example

$250,000 portfolio, $2,500 monthly contribution, $60,000 expenses today, 4% withdrawal assumption, 7% return, 2.5% inflation.

Current FIRE number = $1,500,000. Estimated time ≈ 261 months (21 years 9 months). Portfolio when first reached ≈ $2,572,932 versus an inflated target ≈ $2,566,465.

Important assumptions

  • Expenses are entered in today's dollars; the modeled target rises with inflation.
  • Withdrawal rate is a user-supplied assumption — not a recommendation.
  • Expected return is a hypothetical effective annual assumption.
  • Simulation horizon is capped at 1,200 months (100 years).
  • Taxes, fees, Social Security, pensions, and sequence-of-returns risk are not modeled.

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