About the FIRE Calculator
FIRE stands for Financial Independence, Retire Early — the idea of saving and investing aggressively enough that your portfolio can sustainably cover your living expenses without needing employment income. This calculator works out your "FIRE number" (the portfolio size needed) from your expected annual expenses and a safe withdrawal rate, then projects how many years of saving and compounding it would take to reach that number from where you are now. It also compares a few different withdrawal rate assumptions side by side, since that single choice meaningfully changes both your target and your timeline. Everything is calculated locally in your browser.
The 4% Rule
Where it comes fromThe Trinity Study (1998) analyzed historical US stock and bond returns and found that withdrawing 4% of a portfolio in the first year, then adjusting that dollar amount for inflation each subsequent year, had a high historical success rate over 30-year retirements.
The "25x" shortcutA 4% withdrawal rate is mathematically the same as needing 25 times your annual expenses saved — dividing by 0.04 is the same as multiplying by 25.
Why early retirees adjust itThe original study modeled 30-year retirements. Someone retiring at 35 might need their money to last 50-60 years, which is why some FIRE planners use 3.5% or even 3% for a larger safety margin.
Real vs nominal returnsUsing a "real" (inflation-adjusted) expected return keeps your expense figure constant in today's dollars for the whole projection, instead of needing to inflate it every year separately — this is why the return input here should already exclude inflation.
What this doesn't includeInvestment fees, taxes on withdrawals, Social Security or pension income, healthcare cost changes, and the reality that real returns vary year to year rather than staying constant.
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