What Is a FIRE Calculator?

FIRE stands for Financial Independence, Retire Early — the idea that once your investments can cover your living costs forever, work becomes optional, whatever your age. This calculator answers the movement’s two central questions. First, how big does the pile need to be? That’s your FIRE number: 25 times your annual expenses. Second, how long until you get there? Enter your current invested savings, how much you add each year, and an expected return, and a year-by-year simulation counts down to the crossover.

How It Works

The 25× multiplier is simply the famous 4% withdrawal rule turned inside out. If a portfolio can historically sustain withdrawals of about 4% a year, then the portfolio you need is your spending divided by 4% — which is the same as multiplying by 25:

Notice what’s not in the formula: your income. FIRE runs on the gap between what you earn and what you spend. Cutting $1,000 from annual spending does double duty — it frees up $1,000 more to invest and shrinks your target by $25,000. The simulation then compounds your balance at the expected return and adds your savings at each year-end until the balance crosses the target.

Worked Example: $50,000 of Spending

Suppose you spend $50,000 a year, giving a FIRE number of $1,250,000. You’ve invested $100,000 so far, save $30,000 a year, and assume a 7% return. The simulation crosses the line in about 18 years, finishing near $1,357,964 — the final year’s compounding overshoots the target. Trim spending to $40,000 and save the extra: with a $1,000,000 target, $50,000 of savings, and $25,000 saved yearly, independence arrives in about 18 years too — but supporting a leaner life. The lever that matters most is the savings rate: the fraction of income you keep, not the size of the paycheck.

Lean FIRE, Fat FIRE, and the Flavors In Between

The community has named points along the spectrum. Lean FIRE targets a frugal budget — a smaller multiple of a deliberately low spending number, reachable sooner but with little slack. Fat FIRE funds a comfortable, even indulgent retirement, demanding a far larger portfolio. Coast FIRE means you’ve saved enough early that compounding alone will finish the job by traditional retirement age, so you only need to cover current expenses. Barista FIRE blends part-time work with partial portfolio support. Whichever flavor fits, the calculator’s math is the same — only the expense line changes.

Common Mistakes to Avoid

The biggest error is lowballing expenses — your FIRE budget must include healthcare (a major cost before Medicare eligibility), taxes on withdrawals, and irregular hits like roofs and transmissions. Second, using today’s dollars for the target but nominal returns for growth; be consistent, or use a real (after-inflation) return of perhaps 4–5% instead of 7%. Third, treating 25× as bulletproof: an early retirement may need to survive 50+ years, and many planners prefer a more conservative multiple for very long horizons. This calculator provides educational estimates only, not financial or tax advice — consult a qualified professional before quitting anything.

Frequently Asked Questions