FIRE number calculator
A FIRE number is a portfolio target built around the spending it needs to support. It is a useful shorthand, but a single balance cannot describe an entire retirement plan.
Enter annual portfolio-funded spending and an initial withdrawal-rate assumption to calculate a target. This is not financial advice.
The FIRE number formula
FIRE number = annual portfolio-funded spending ÷ initial annual withdrawal rate
Use the withdrawal rate as a decimal in the formula: 4% becomes 0.04. It describes the first year’s withdrawal as a share of the starting portfolio. It is not the annual investment return.
Enter your own annual portfolio-funded spending and withdrawal assumption in the tool above. The target is spending ÷ rate; it is arithmetic, not a guarantee.
What belongs in annual spending?
Use the amount that must come from investments. Include an allowance for taxes on withdrawals where relevant, as well as healthcare, housing and irregular costs. Avoid counting money earmarked for a separate near-term purchase as retirement capital.
If you expect income from work, a pension or Social Security, consider both its amount and start date. Subtracting income that starts much later from every year’s spending can leave the earlier years underfunded. This calculator does not model those phases.
Compare withdrawal assumptions
Compare withdrawal assumptions with your own spending in the calculator. Lower rates raise the target; higher rates lower it. Rates are assumptions, not recommendations.
A higher withdrawal rate gives a smaller target mathematically. It does not make the withdrawals safer. The formula does not test retirement length, investment mix, variable returns or the order of gains and losses.
Keep all amounts on the same basis. A target expressed in today’s dollars must be compared with an inflation-adjusted projection, not a future nominal balance.
A FIRE number is not a Coast FIRE number
Your FIRE number is the target at the point withdrawals are meant to begin. Your Coast FIRE number is the smaller—or, under some negative-growth assumptions, larger—balance needed earlier to reach that target without further deposits.
For a no-contribution projection, the Coast FIRE calculator discounts the target by the assumed real growth over the remaining years. Read the calculation steps to see how the two numbers connect.
Does this calculator tell me I can quit work?
No. It calculates a target from inputs you choose. It does not evaluate investment suitability, access to accounts or whether a withdrawal plan will last.
Model and transparency
Last updated: 6 November 2026. Deterministic annual calculations, not a historical success test. This is not financial advice.
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