FIRE Number Calculator
Enter your annual expenses, current savings, and savings rate to calculate your FIRE number for Lean, Standard (4% rule), and Fat FIRE. See your progress bar and how many years you'd save by investing more each year.
What you spend per year in retirement
Historical S&P 500 real return ~7%
Lean FIRE
3.5% withdrawal
—
— years
FIRE (4% rule)
4% withdrawal
—
— years
Fat FIRE
5% withdrawal
—
— years
What if I save more? (vs. 4% rule target)
| Extra / year | Years to FIRE | Years saved |
|---|
Understanding Your FIRE Number
Financial Independence, Retire Early (FIRE) rests on a simple principle: once your investment portfolio generates enough in returns to cover your annual spending, you no longer need to work for money. Your FIRE number — the portfolio size needed — depends entirely on two variables: how much you spend and how much you safely withdraw each year.
The 4% rule is the most widely cited guideline: a portfolio of 25× your annual spending has historically sustained 30-year retirements with very high probability. If you plan to retire at 40 and live to 90, a 50-year window may call for a more conservative 3.5% rate (28.6× annual spending) — that's Lean FIRE.
The most powerful lever in your FIRE timeline isn't your return rate — it's your savings rate. Going from saving $20,000/year to $25,000/year can shave 3–6 years off your timeline depending on your starting balance. Use the sensitivity table above to see exactly how much each extra $1,000 of annual savings buys you in time.
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Frequently Asked Questions
What is a FIRE number? ▼
Your FIRE number is the total investment portfolio you need to sustain your retirement spending indefinitely. It's calculated by dividing your annual expenses by your safe withdrawal rate (SWR). At 4% SWR: FIRE number = annual expenses × 25.
What is the 4% rule? ▼
The 4% rule (the "Bengen Rule") states that a retiree can withdraw 4% of their portfolio in the first year of retirement, then adjust for inflation each year, and have a very high probability of not running out of money over a 30-year retirement. It's based on William Bengen's 1994 research using historical US market data.
What is the difference between Lean, Standard, and Fat FIRE? ▼
Lean FIRE uses a 3.5% withdrawal rate — a more conservative approach for those living frugally or retiring early with a long runway. Standard FIRE uses the classic 4% rule. Fat FIRE uses 5%, implying a larger lifestyle budget or a higher risk tolerance for a shorter retirement period.
What annual return should I use? ▼
The historical average real return (after inflation) of a diversified US stock portfolio is approximately 7% per year. For a global diversified portfolio, 6–7% is a commonly used planning figure. More conservative planners use 5–6% to account for sequence-of-returns risk.
Does this account for inflation? ▼
The 7% default return already approximates a real return (nominal ~10% minus ~3% historical inflation). If you use a nominal return (e.g., 10%), your expenses should also be entered in nominal future dollars. For simplicity, use real return (7%) and today's spending figures.
What is Coast FIRE? ▼
Coast FIRE is when you've saved enough that — without any further contributions — your portfolio will grow to your FIRE number by traditional retirement age (65+). You only need to cover your current expenses; you stop investing aggressively. A Coast FIRE calculator requires your target age, which this tool doesn't model, but the standard FIRE number is the same target.
How accurate is this calculator? ▼
This is a planning tool, not a guarantee. It assumes a constant annual return and no sequence-of-returns risk. Real markets are volatile — a bad decade early in retirement can materially affect outcomes. For comprehensive planning, consider Monte Carlo simulations or consult a fee-only financial planner.