FIRE Number Calculator
Enter your target annual spending in retirement to find your FIRE number — the portfolio size that supports it indefinitely at your chosen withdrawal rate — plus how long it takes to get there at your current savings rate.
FIRE number at other withdrawal rates
How this is calculated
Your FIRE number is target annual spending divided by your withdrawal rate (spending ÷ withdrawal rate — e.g. 40,000 ÷ 4% = 1,000,000, in whatever currency you entered spending in). This is deliberately currency-agnostic: the math is a ratio, so it works identically whether you're thinking in dollars, euros, or any other currency — enter your numbers in your own currency and the result comes back in the same one.
Lean, Regular and Fat FIRE are classified here by comparing your target retirement spending to your OWN current annual expenses, not against a fixed currency threshold. A fixed dollar cutoff (the way most FIRE calculators define 'Fat FIRE') means something completely different in a low cost-of-living country than a high one — comparing your target against your own baseline keeps the label meaningful regardless of where you live.
Time to reach your FIRE number runs a real month-by-month simulation of your current portfolio compounding at your expected return plus your monthly contribution, stopping the month your simulated portfolio first reaches the target — not a shortcut formula, since contribution size relative to portfolio size changes how much compounding vs. contributions does the work over time.
The withdrawal-rate comparison table shows how sensitive your FIRE number is to that one assumption — a lower, more conservative withdrawal rate requires a meaningfully larger number for the exact same spending target, which is worth seeing side by side rather than committing to a single rate upfront.
Frequently asked questions
What withdrawal rate should I use?
4% is the most commonly cited starting point, based on historical safe-withdrawal-rate research, though some planners now use a more conservative 3-3.5% for longer retirements or more uncertain markets. Comparing a few rates side by side (shown above) is more useful than treating any single rate as definitively correct.
How are Lean, Regular and Fat FIRE defined here?
By comparing your target retirement spending to your own current annual expenses: roughly 30% below your current spending or more is classified Lean, roughly 30% above is Fat, and anything in between is Regular. This is a convention for this calculator, not a universal definition — other sources sometimes use fixed currency thresholds instead, which don't translate well across countries.
Does this work if I don't use US dollars?
Yes — every input and output here is just a number, with no currency conversion or fixed-currency assumption built in anywhere. Enter your figures in your own currency and the FIRE number, classification and time-to-reach all come back consistent with that same currency.
Does this account for inflation?
Not separately — the return rate you enter is applied directly to your entered spending figure. If your spending target is already in today's purchasing power, use a return rate that's already adjusted for expected inflation (a 'real' return) rather than a raw nominal market average.
Sources
- Trinity Study (1998) and related safe-withdrawal-rate research — basis for the common 4% withdrawal-rate convention
- FIRE (Financial Independence, Retire Early) community terminology for Lean/Regular/Fat FIRE variants
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Disclaimer
This tool provides an estimate for informational purposes based on the figures and return assumption you enter and isn't financial advice. Actual investment returns vary year to year and aren't guaranteed, and a sustained downturn early in retirement can affect a fixed withdrawal-rate plan more than the long-run average return alone suggests.
Last updated 2026-11-05.