How Much Do You Need to Retire? Calculating Your FIRE Number
“How much do I need to retire?” is the most important question in personal finance — and most people either avoid it or answer it with a vague, uncomfortable shrug. The answer is not a mystery. It is arithmetic. Knowing your number transforms retirement from an abstract future aspiration into a specific, trackable target you can work toward methodically. This article explains how to calculate it precisely, as part of our complete personal finance series.
- → Your retirement number = annual retirement expenses × 25 (based on the 4% safe withdrawal rate)
- → The 4% rule has held across virtually all historical market conditions over 30-year periods — but may be too aggressive for 40–50 year early-retirement horizons
- → State pension entitlements (AOW in the Netherlands, state pension elsewhere) significantly reduce the private portfolio needed
- → Your spending in retirement is likely to be lower than working-life spending — but healthcare costs tend to rise with age
- → Sequence-of-returns risk — retiring into a bear market — is the primary threat to the 4% rule and can be mitigated through flexible withdrawal strategies
The Core Formula
The standard retirement number calculation comes from the 4% safe withdrawal rate, derived from the Trinity Study. The logic: a portfolio invested in a balanced mix of equities and bonds has historically been able to sustain annual withdrawals of 4% of the initial portfolio value — adjusted upward for inflation each year — over a 30-year period without depleting the principal in the vast majority of historical scenarios.
Working backwards gives you the formula:
FIRE Number = Annual Retirement Expenses × 25
Or equivalently: Annual Retirement Expenses ÷ 0.04 = Required Portfolio.
Step 1: Calculate Your Annual Retirement Expenses
The most important input — and the most frequently miscalculated — is what you will actually spend in retirement. Most people either guess too high (anchoring on current spending) or too low (ignoring healthcare, travel, and lifestyle upgrades they’ve been deferring). A realistic retirement budget should include:
| Category | Typical Monthly Cost | Notes |
|---|---|---|
| Housing (rent or maintenance) | €800–€1,500 | Lower if mortgage-free |
| Food & groceries | €400–€700 | May rise — more time at home |
| Transport | €200–€500 | May fall — no commuting |
| Healthcare | €150–€400 | Rises significantly with age |
| Travel & leisure | €300–€1,000 | Often underestimated |
| Utilities & insurance | €200–€350 | Relatively stable |
| Miscellaneous | €200–€400 | Buffer for unexpected costs |
Step 2: Factor in State Pension Entitlements
In the Netherlands, the AOW (Algemene Ouderdomswet) provides a state pension of roughly €1,350–€1,550 per month for a single person (2026 figures) from age 67. This significantly reduces the private portfolio required.
“Your AOW effectively reduces your FIRE number by €400,000–€450,000 in present value terms. For traditional retirement planners, this is enormous. For early retirees who cannot access AOW until 67, the full portfolio must bridge the gap.”
If you plan to retire at 45 and receive AOW at 67, you need two calculations: a portfolio large enough to fund 22 years from 45 to 67, plus a smaller portfolio to supplement AOW from 67 onwards. The total is substantially less than funding 40+ years entirely from private capital — which is why traditional retirement at 65–67 requires a much smaller nest egg than early FIRE.
Step 3: Adjust for Your Time Horizon
The 4% rule was validated for 30-year retirement horizons. If you retire at 40 and live to 90, you have a 50-year horizon — for which historical data is less reassuring. Many FIRE practitioners use a 3–3.5% withdrawal rate for early retirement, which implies a 29–33× multiple rather than 25×.
Traditional retirement (65+): 4% withdrawal rate (25× expenses) — well-supported by historical data over 25–30 year horizons.
Early retirement (50–64): 3.5% (28–29× expenses) — more conservative to account for longer horizon.
Very early FIRE (under 50): 3–3.25% (31–33× expenses) — prudent for 40–50 year horizons, or supplement with Barista FIRE income.
Sequence-of-Returns Risk: The Hidden Threat
The biggest practical risk to any withdrawal strategy is retiring into a severe bear market in the first few years. If your portfolio drops 40% in year one of retirement and you simultaneously withdraw 4%, you are withdrawing a much larger percentage of the remaining portfolio. This can permanently impair the portfolio’s ability to recover — even if markets subsequently perform well.
Mitigation strategies include: maintaining 1–2 years of expenses in cash so you never have to sell equities during a downturn; flexible withdrawal (reducing spending 10–15% in bad market years); or Barista FIRE (maintaining a small income stream that covers essential expenses during downturns). These approaches dramatically improve the resilience of a retirement portfolio without requiring a larger nest egg. They connect to the broader investing framework in our FIRE complete guide.
Your retirement number is not a mystery — it is your annual retirement expenses multiplied by 25 (or 28–33 for early retirement). Calculate it today. Then track your progress toward it monthly. The psychological effect of having a specific target — and watching your portfolio close the distance — is one of the most powerful motivators in personal finance. Every month you invest, the gap shrinks from both ends: the portfolio grows, and the habit of living on less demonstrates that your required retirement number may be lower than you initially assumed.
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