FIRE Number Calculator
Your “FIRE number” — the portfolio size where you could theoretically live off withdrawals indefinitely — is the central number in the Financial Independence, Retire Early movement. It’s built on the 4% rule (also called the safe withdrawal rate), which comes from historical research suggesting a portfolio can sustain a 4% annual withdrawal, adjusted for inflation, over a 30-year retirement with a high probability of not running out. This calculator finds your FIRE number from your annual expenses, then estimates how many years until your current savings and contributions get you there.
Where the 4% Rule Comes From
The 4% figure traces back to the “Trinity Study,” academic research that tested how various withdrawal rates would have performed across rolling historical 30-year periods of U.S. market returns. A 4% initial withdrawal, increased with inflation each year, held up in the large majority of those historical periods without depleting the portfolio — which is mathematically the same as saying you need roughly 25 times your annual expenses saved (since 1 ÷ 0.04 = 25). Lowering your withdrawal rate to 3.5% or 3% makes the number more conservative — 28.6x and 33.3x annual expenses respectively — for those planning a longer or more uncertain retirement horizon.
Why Your Expense Number Matters More Than Your Income
Because the FIRE number is built entirely from annual expenses, not income, two people earning the same salary can have wildly different FIRE numbers depending on their lifestyle. This is also why cutting spending has a double effect on your timeline: it lowers the target you're saving toward and frees up more money each month to save, which is why many in the FIRE community focus heavily on optimizing recurring expenses rather than only chasing a higher income.
A Few Practical Notes
The 4% rule is a historical guideline, not a guarantee — it was tested against past U.S. market conditions, and future returns, inflation, and sequence-of-returns risk (poor returns early in retirement) could all affect real-world outcomes. It also doesn't account for Social Security, which can reduce the portfolio withdrawal actually needed later in retirement. Many FIRE planners use a lower 3–3.5% rate specifically to build in a margin of safety for a retirement that could last 40+ years. Explore variations of this idea with our upcoming Coast FIRE and Barista FIRE calculators.
Freedom Wealth Lab Apps provides general educational tools, not personalized financial advice. Read our full Disclaimer and Affiliate Disclosure. The 4% rule is based on the “Trinity Study” (Cooley, Hubbard & Walz, 1998) using historical U.S. market data — treat the default rate as a reference point for any market, not a guarantee.
