FIRE Number Calculator

Financial Independence, Retire Early (FIRE) communities popularized a portfolio target: annual spending divided by a safe withdrawal rate (SWR). At 4%, the multiplier is 25× annual expenses — spend $48,000/year → $1,200,000 portfolio ($48,000 ÷ 0.04). Lower withdrawal rates raise the target; 3.5% implies about 28.6× expenses.

The 4% rule traces to historical US stock/bond portfolio studies (Trinity-style analysis) over 30-year retirement windows. It assumes inflation-adjusted withdrawals, rebalancing, and US market history — not guarantees for every country, every era, or every retiree lifespan.

Defaults match: $48,000 annual expenses at 4% withdrawal → $1,200,000 FIRE number. Change withdrawal to 3.5% and the target rises to about $1,371,429 — conservative planners often model 3–3.5% for long retirements, early FIRE exits, or sequence-of-returns risk.

Expenses should reflect the lifestyle you plan in retirement, not current gross income. Exclude payroll taxes and retirement savings from the expense figure if those stop. Include health insurance, travel, and replacement vehicles — underestimating spending inflates false confidence.

Social Security, pensions, rental income, and part-time work reduce the portfolio you need — this calculator ignores them, showing gross portfolio from expenses only. Subtract expected other income manually from expenses before running, or treat the result as a pre-offset estimate.

Common mistakes include using 4% as prophecy in low-yield eras, ignoring taxes on withdrawals from pre-tax accounts, and comparing FIRE number to gross 401(k) balance without noting tax haircut on traditional accounts.

Coast FIRE variants assume you stop contributing once the portfolio reaches a level that compounds to the full FIRE number by traditional retirement age — this calculator does not model two-phase accumulation.

Geographic arbitrage lowers expenses in FIRE math — moving from high-cost to lower-cost area reduces the target; rerun with post-move spending estimates.

Barista FIRE and partial work cover part of expenses — subtract expected part-time earnings from annual spending before dividing by withdrawal rate.

Healthcare before Medicare is a common FIRE budget gap — add premium and out-of-pocket estimates to annual expenses before calculating the number.

Sequence-of-returns risk hits early retirees harder — withdrawing in a down market permanently impairs the portfolio; conservative withdrawal rates partly address that fear.

Lean FIRE versus fat FIRE is spending choice — same formula, different expense input; luxury travel belongs in the numerator if you will spend on it.

Withdrawal rate sensitivity: $48,000 spending at 3% needs $1.6M versus $1.2M at 4% — slide the withdrawal field to stress-test, not only 4%.

Inflation raises nominal spending over decades — FIRE numbers for age-40 exit need higher future expenses or lower real withdrawal assumptions.

Paid-off home reduces expenses but home equity is illiquid — some planners exclude home equity from FIRE portfolio while counting lower rent-free living costs.

Coast FIRE variant: if you already have enough invested to grow to FIRE by 65 without new contributions, you may only need to cover current expenses — different math than this full-expense divider.

Part-time work in early retirement reduces withdrawals — subtract expected earned income from expenses before applying the withdrawal divisor.

Bond-heavy portfolios may justify lower withdrawal rates than stock-heavy histories — rate choice is personal stress tolerance, not one universal answer.

Dynamic spending rules cut withdrawals after bad market years — static 4% math ignores that flexibility used in real retirements.

Mortgage paid off before FIRE lowers annual expenses — rerun with lower expense input after housing cost drops to zero.

Sequence risk is worst in the first decade of retirement — early FIRE exits face longer exposure; lower withdrawal rates partly address that fear.

Pension income with cost-of-living adjustments reduces portfolio withdrawal need — subtract COLA pension from expenses before dividing by rate.

Limits: illustration only — not retirement, tax, or investment advice. Does not model healthcare before Medicare, long-term care, or dynamic spending cuts in down markets.