Annual spendingHigh modeled impact
Higher input raises the modeled result
Spending not covered by other income must be funded by the portfolio.
Retire · Portfolio target
FIRE Number Calculator
Estimate the portfolio implied by your annual spending gap and withdrawal-rate assumption—then see how sensitive that modeled target is to the rate you choose.
Educational scenario Deterministic calculation
Your result
Modeled FIRE target
$1,250,000
The portfolio implied by the spending gap and withdrawal-rate assumption entered.
Annual spending$60,000
Other annual income$10,000
Portfolio-funded spending$50,000
Withdrawal-rate assumption4.00%
Spending multiple25.00×
At a 4.00% withdrawal assumption, the modeled portfolio equals 25.00 times the annual spending it must fund.
Current portfolio progress40.00%
Current portfolio$500,000
Modeled target$1,250,000
Gap remaining$750,000
Progress is a comparison with this modeled target, not confirmation of retirement readiness.
Withdrawal-rate sensitivity
One spending gap, five modeled targets
Each bar uses the same portfolio-funded spending. The only change is the withdrawal-rate assumption; no rate is presented as the correct choice.
3.0%
$1,666,667
3.5%
$1,428,571
4.0%Current input
$1,250,000
4.5%
$1,111,111
5.0%
$1,000,000
For $50,000 of annual portfolio-funded spending: 3% implies about $1.67 million; 3.5% about $1.43 million; 4% $1.25 million; 4.5% about $1.11 million; and 5% $1 million.
Through the Lens
What drives this result?
Controlled, deterministic sensitivity around your current inputs reveals which assumptions move the modeled FIRE target most.
Withdrawal rateHigh modeled impact
Higher input lowers the modeled result
A lower assumed withdrawal rate requires a larger target.
Other annual incomeLow modeled impact
Higher input lowers the modeled result
Other income reduces the spending gap the portfolio must fund.
High modeled impact means an input changes this output substantially around the current scenario. Rankings compare controlled 10% input changes; they do not measure risk, probability, personal importance, controllability, suitability, advice, or forecasts.
Meaning
What this means
The target connects a spending gap to a withdrawal assumption.
A modeled target of $1,250,000 at a 4.00% withdrawal assumption means that percentage of the portfolio equals $50,000 per year.
4% × $1,250,000=$50,000
That amount fills the modeled gap between $60,000 of annual spending and $10,000 of other annual income.
Implication
A lower withdrawal-rate assumption produces a larger required portfolio. A higher rate produces a smaller modeled target but represents a more aggressive withdrawal assumption.
The calculator does not recommend a rate and does not determine whether someone is ready to retire.
Methodology
How the calculator works
Portfolio-funded spending
max(annual spending − other annual income, 0)Modeled FIRE target
portfolio-funded spending ÷ (withdrawal rate ÷ 100)Portfolio multiple
100 ÷ withdrawal rateOptional progress
current invested portfolio ÷ modeled FIRE target × 100The progress bar is capped visually at 100%, while the numerical percentage can exceed 100%. The current portfolio never changes the target.
Guardrails
Assumptions and limitations
This simplified scenario does not model:
- Sequence-of-returns risk, changing returns, or market crashes
- Inflation changes, taxes, investment fees, or changing spending
- Longevity, healthcare costs, or one-time expenses
- Pension uncertainty or government-benefit changes
- Future changes to the withdrawal rate
Withdrawal rates are assumptions—not guarantees.
This is an educational estimate, not a forecast, retirement-readiness assessment, or personalized financial advice.
Known-answer checks
Examples used to validate the engine
Standard case$60,000 spending − $10,000 income at 4% = a $1,250,000 target and 25× multiple.
Income covers spendingWhen other income equals or exceeds spending, portfolio-funded spending and the target are $0.
Rate sensitivityFor the same spending gap, 3% produces a larger target than 4%, while 5% produces a smaller target.
Progress case$500,000 toward $1,250,000 equals 40% progress and a $750,000 modeled gap.
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