4% Rule Calculator: either direction.
The rule that started the FIRE movement: withdraw 4% of your portfolio in year one, adjust for inflation after, and your money historically lasts 30+ years. Pick a direction — start with money or with spending.
The 4% rule comes from the Trinity Study (Cooley, Hubbard, and Walz, 1998), which back-tested rolling 30-year retirement windows from 1926 through 1995. The rule says: in year one of retirement, withdraw 4% of your portfolio; every year after, withdraw that same dollar amount adjusted for inflation. Across nearly every historical window — including the Great Depression, the 1970s stagflation, and the dot-com bust — a 50/75% stock-bond portfolio survived 30+ years at a 4% initial rate roughly 95% of the time. Lower rates (3%, 3.5%) approach 100% success; higher rates (4.5%, 5%) drop toward 70%. The 4% rule is the foundation of every FIRE number: portfolio ÷ SWR × spending. Lower the SWR and the math demands a bigger portfolio but a much higher survival odds. Raise it and you retire sooner, with more risk.
Read the full explainer →Three steps to your number
- 1Start in reverse modeThe engine opens on “I have savings → what can I spend?” with a $1,000,000 portfolio and 4% SWR pre-loaded. Drag the portfolio slider to match your savings.
- 2Adjust the withdrawal rateSlide between 3% (safest, ~99% historical success), 4% (Trinity Study default, ~95%), and 5% (riskiest, ~70%). Each step reshapes your safe withdrawal.
- 3Toggle to forward mode if you want the inverseSwitch to “I know my spending → my number” to invert the math: enter annual expenses and see the portfolio you need saved.
Your numbers
The 4% rule comes from the Trinity Study (Cooley et al., 1998): a 30-year retirement starting with a 4% initial withdrawal rate, adjusted annually for inflation, succeeded ~95% of the time across historical market periods. Lower SWRs (3% / 3.5%) approach 100% historical success.
A $1,000,000 portfolio at 4.0% SWR sustained this spending in ~95% of historical 30-year periods (Trinity Study). It's a rule of thumb, not a guarantee. Invert the math: your FIRE number for this spending level is $1,000,000 (25.0× spending).
| SWR | Annual withdrawal | Monthly withdrawal |
|---|---|---|
| 3.5% | $35,000 | $2,917/mo |
| 4% | $40,000 | $3,333/mo |
| 4.5% | $45,000 | $3,750/mo |
The 4% rule comes from the Trinity Study (Cooley et al., 1998): a 30-year retirement starting with a 4% initial withdrawal rate, adjusted annually for inflation, succeeded ~95% of the time across historical market periods. Lower SWRs (3% / 3.5%) approach 100% historical success.
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The math, explained.
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How this number is calculated
Annual withdrawal = Portfolio × SWR. Monthly = Annual ÷ 12. The 30-year success rates come from the Trinity Study’s historical backtests of rolling 30-year windows from 1926–1995.
This page is a preset route of the FIRE Number calculator engine (PRD §5.0): the engine opens in reverse mode — “I have savings → what can I spend?” — with a $1,000,000 portfolio and a 4% SWR pre-loaded. The same The Plan slider and SWR comparison table render underneath. Read the 4% rule explained or the Trinity Study breakdown. Source: Cooley, Hubbard, and Walz, “Portfolio Success Rates” (1998, updated).