Understanding your FIRE results
The withdrawal rate chosen sets the target's conservatism. These reference points summarize the research behind common choices.
| Withdrawal rate | Multiple of expenses | Research context |
|---|---|---|
| 4% | 25× | Bengen 1994; Trinity 1998 — historically survived all US 30-year periods tested |
| 3.5% | ≈ 28.6× | Common early-retirement adjustment for horizons beyond 30 years |
| 3% | ≈ 33.3× | Very conservative; favored when long horizons meet cautious return expectations |
| 5%+ | ≤ 20× | Elevated historical failure risk over 30 years in adverse sequences |
- The 4% rule assumed a 30-year retirement, US historical returns, a stock-bond portfolio, no fees and no taxes; early retirees with 40+ year horizons face materially different odds, and several researchers suggest lower rates for those cases.
- Sequence-of-returns risk — poor markets in the first retirement years — can deplete a portfolio even when average returns match the assumption; it is the main mechanism behind historical failures of higher withdrawal rates.
- The years-to-FIRE projection assumes constant contributions and a smooth constant return, and excludes taxes, fees, pensions and state benefits; a licensed adviser can model a specific situation properly.
What is FIRE?
FIRE stands for Financial Independence, Retire Early — a planning framework in which work becomes optional once invested assets can sustainably fund living expenses. The core arithmetic is the FIRE number: annual expenses divided by a safe withdrawal rate. At the conventional 4% withdrawal rate, the FIRE number is 25 times annual expenses; someone spending $40,000 per year would target $1,000,000.
The 4% figure originates in William Bengen's 1994 study in the Journal of Financial Planning, which tested withdrawal rates against every historical 30-year period of US stock and bond returns since 1926 and found 4% (inflation-adjusted annually) survived even the worst sequences. The 1998 Trinity Study (Cooley, Hubbard and Walz) reached similar conclusions across portfolio mixes. Both studies assumed a 30-year horizon — a key caveat for early retirees who may need 40–60 years.
Criticisms of the rule are well documented: it is based on US historical returns that may not repeat; longer horizons and today's valuations argue for lower rates (researchers such as Wade Pfau have suggested 3–3.5% for early retirement); it ignores fees, taxes and irregular spending such as healthcare; and rigid inflation-adjusted withdrawals do not reflect how people actually adapt spending. Many planners treat the 25× target as a milestone for flexible decision-making rather than a precise finish line.
How to use this FIRE calculator
- Enter your expected annual expenses in retirement — the figure the portfolio must fund each year.
- Enter your current invested savings and your monthly saving amount.
- Set the expected annual return on investments; long-run conservative planning assumptions are commonly 5–7% nominal.
- Set the safe withdrawal rate — 4% is the classic Bengen/Trinity figure; 3–3.5% is a more conservative choice for very long retirements.
- Read your FIRE number, current progress percentage, and the estimated years to reach the target at the assumed return.
The FIRE formula
The FIRE number divides annual expenses by the withdrawal rate; at 4% this is exactly 25× expenses. Years to FIRE come from compounding the current savings and monthly contributions forward at the assumed return until the target is reached.
Worked example: $40,000 of annual expenses at a 4% withdrawal rate gives a FIRE number of 40,000 ÷ 0.04 = $1,000,000. With $100,000 already invested (10% progress) and $2,000 saved monthly at a 6% assumed return, the balance reaches $1,000,000 in roughly 207 months — about 17.2 years. At a 3.5% withdrawal rate the target rises to about $1,143,000 and the timeline lengthens.
Common mistakes
- Using current expenses instead of expected retirement expenses, which may differ substantially (healthcare, housing, travel).
- Applying the 30-year-tested 4% rule unchanged to a 50-year early retirement without adjusting the rate downward.
- Ignoring taxes on withdrawals — a $40,000 spending need can require noticeably more in gross portfolio withdrawals.
- Treating the years-to-FIRE estimate as precise; it is highly sensitive to the assumed return and to market sequences.
- Forgetting fees: a 1% annual fee effectively reduces the sustainable withdrawal rate by a comparable amount.
Preguntas frecuentes
What is a FIRE number?
A FIRE number is the portfolio size at which investments can sustainably fund annual living expenses — calculated as annual expenses divided by a safe withdrawal rate. At the classic 4% rate this equals 25 times annual expenses: spending of $40,000 per year implies a $1,000,000 target. At a more conservative 3.5% the multiple rises to about 28.6×.
Where does the 4% rule come from?
Financial planner William Bengen published it in the Journal of Financial Planning in 1994, after testing withdrawal rates against every rolling 30-year period of US stock and bond history since 1926 and finding that 4%, adjusted for inflation each year, survived even the worst starting points. The 1998 Trinity Study by Cooley, Hubbard and Walz independently supported the guideline across several portfolio allocations.
What are the criticisms of the 4% rule?
The main criticisms: it is derived from US historical data that may overstate future returns; it was tested for 30-year horizons, while early retirees may need 40–60 years; it ignores investment fees and taxes; and it assumes rigid inflation-adjusted withdrawals rather than the flexible spending real retirees practice. Researchers including Wade Pfau have argued for 3–3.5% rates for long early retirements and international portfolios.
What is sequence-of-returns risk?
Sequence-of-returns risk is the danger that poor market returns early in retirement — while withdrawals are being taken — permanently impair a portfolio, even if long-run average returns turn out fine. Withdrawals during a downturn lock in losses that later recoveries cannot fully repair. It is the principal reason a portfolio with a 7% average return cannot safely support a 7% withdrawal rate.
How long will it take me to reach FIRE?
It depends on the gap between savings and target, the savings rate, and the assumed return. For example, from $100,000 toward a $1,000,000 target, saving $2,000 monthly at an assumed 6% return takes roughly 17 years. Because the savings rate controls both accumulation speed and (via expenses) the target itself, raising the savings rate shortens the timeline from both ends.
Does the FIRE number include Social Security or pensions?
No. This model funds all expenses from the portfolio alone. Expected Social Security, state pensions or annuity income can be subtracted from annual expenses before dividing by the withdrawal rate, which lowers the required portfolio — though early retirees face years before such benefits begin, and benefit rules change. Comprehensive planning for a specific case is a matter for a licensed adviser.
Referencias
- Bengen WP. Determining withdrawal rates using historical data. Journal of Financial Planning 1994; 7(4): 171–180.
- Cooley PL, Hubbard CM, Walz DT. Retirement savings: choosing a withdrawal rate that is sustainable. AAII Journal 1998; 20(2): 16–21. (The 'Trinity Study'.)
- Pfau WD. An international perspective on safe withdrawal rates from retirement savings. Journal of Financial Planning 2010; 23(12): 52–61.
- Kitces M, Pfau WD. Reducing retirement risk with a rising equity glide path. Journal of Financial Planning 2014; 27(1): 38–45.
- Federal Reserve Bank of St. Louis. Historical US stock, bond and inflation data. FRED Economic Data (fred.stlouisfed.org).