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Financial Independence, Retire Early — 4% rule
The FIRE movement — Financial Independence, Retire Early — centers on one key figure: your FIRE number. This is the total amount of invested wealth you need to never have to work again. The math comes from the Trinity Study, which found that a 4% annual withdrawal rate has historically sustained a portfolio indefinitely. To find your FIRE number, simply multiply your expected annual expenses by 25. If you spend $50,000 per year, your FIRE number is $1,250,000.
That single formula changes how people think about money. Instead of counting down years to a standard retirement age, you focus on building a portfolio large enough to fund your lifestyle forever. The 4 percent rule accounts for a balanced portfolio of stocks and bonds, historical market returns, and inflation — giving you a realistic, battle-tested target rather than a guess.
Using an early retirement calculator like the one on this page, you can plug in your current savings, monthly contributions, expected investment return, and annual spending to see exactly how many years stand between you and financial independence.
The timeline to FIRE depends heavily on your savings rate — the percentage of your income you save and invest each month. Someone saving 10% of their income might need 40+ years to retire. Someone saving 50% can often reach financial independence in under 17 years, regardless of their income level. This is the core insight of the FIRE movement: your savings rate matters far more than your salary.
For example, if you currently have $100,000 saved, contribute $2,000 per month, and expect a 7% average annual return, you could reach a $1,250,000 FIRE number in approximately 16 years. Bump that monthly contribution to $3,000, and the timeline drops to around 12 years. Small changes in your savings rate create dramatic differences in your projected retirement date.
A financial independence calculator also shows you the power of starting early. Beginning at age 25 versus 35 can mean the difference between retiring at 45 or working until 55. The wealth projection feature lets you visualize exactly how your portfolio grows year by year, so you can see compound growth in action rather than just trusting the math blindly.
FIRE is not one-size-fits-all. There are several variations — Lean FIRE targets a frugal lifestyle with a smaller portfolio (often under $1,000,000), Fat FIRE aims for a comfortable or even luxurious retirement requiring $2,000,000 or more, and Barista FIRE involves working part-time to cover some expenses while drawing smaller amounts from investments. Knowing which version fits your goals helps you set a realistic and motivating target.
The most effective way to accelerate your timeline is to attack both sides of the equation: increase income through career growth or side income, and reduce annual expenses by cutting high-cost lifestyle choices. Even trimming $5,000 from your yearly spending lowers your FIRE number by $125,000 — and means less you have to save overall.
At simple-calculator.online, this FIRE calculator handles the heavy lifting so you can focus on the strategy. Run different scenarios, adjust your assumptions, and find the path to financial independence that fits your actual life.
Yes, for most planning purposes. The Trinity Study tested this rule across decades of market history including recessions and crashes. A 4% withdrawal rate sustained a balanced portfolio over 30-year periods in over 95% of historical scenarios. For very early retirees planning for 40+ years, some experts suggest using 3.5% to be more conservative.
A 6–7% annual return after inflation is a commonly used assumption for a diversified stock and bond portfolio. The S&P 500 has historically averaged around 10% before inflation, and around 7% after inflation. Using 6–7% keeps your projection realistic without being overly optimistic.
Typically, your FIRE number refers only to liquid, investable assets — stocks, bonds, index funds, and retirement accounts. A paid-off home reduces your living expenses, which lowers your FIRE number, but the home's value itself is not usually counted in the portfolio you draw from.