The 25× rule explained — your FI number and how to actually hit it
Multiply your annual expenses by 25 to find your retirement number. The math, the assumptions, and the practical adjustments for early retirement.
A retirement-planning shortcut: your needed portfolio = annual expenses × 25. Derived from the 4% safe withdrawal rate.
Example: $50,000/year of expenses requires a $1,250,000 portfolio.
The maximum percentage of a portfolio that can be withdrawn annually (adjusted for inflation) for 30 years with a high probability of not running out. From the Trinity Study (1998).
Financial Independence number — the portfolio size at which work becomes optional because investments cover annual expenses indefinitely.
The 25× rule is the simplest retirement-planning shortcut ever invented. Multiply your annual expenses by 25, and that's the portfolio size you need to retire. It works because of the 4% safe withdrawal rate (1/25 = 4%) — the empirically-tested rate at which a balanced portfolio can sustain inflation-adjusted withdrawals for 30 years.
The basic math
Annual expenses → multiply by 25 → that's your FI number. $30,000/year = $750K. $50,000/year = $1.25M. $80,000/year = $2M. $120,000/year = $3M. The number depends entirely on your spending, not your income.
Where the 4% comes from
In 1998, three Trinity University professors back-tested portfolio survival across every 30-year period in US market history. A 50/50 stock/bond portfolio withdrawing 4% (inflation-adjusted) survived 95%+ of historical periods. The "4% rule" was born — and 1/4% = 25, hence the 25× rule.
The early-retirement adjustment
The 4% rule was tested for 30-year retirements. If you retire at 45 and need 40-50 years of withdrawals, 4% becomes risky. Most early-retirement researchers (Big ERN, Karsten Jeske) recommend 3.25-3.5% — a 28-31× multiplier. Same $50K expenses now requires $1.5-1.6M instead of $1.25M.
The valuation adjustment
Some researchers argue that today's high stock valuations (high CAPE ratios) reduce expected returns. Wade Pfau and Michael Kitces have suggested 3.5-3.8% as more appropriate now. The conservative move: target 28-30× as your "comfortable" FI number, treat 25× as the "lean FI" floor.
How to actually use the rule
(1) Track every expense for 6 months. (2) Multiply average annual spending by 25 (or 28-30 for early retirement). (3) Subtract any guaranteed income (Social Security, pensions) — Social Security at age 67 is roughly $30K/year, equivalent to $750K of portfolio. (4) Use a compound calculator to project when your contribution rate will get you there at 7% real return.
The hidden lever: spending
Cutting $5,000 of annual expenses isn't just $5K saved — it reduces your FI number by $125K (at 25×). Conversely, lifestyle inflation of $5K/year increases the goalpost by $125K. This is why frugality compounds: every dollar of expenses you eliminate is 25 dollars of portfolio you don't need to accumulate.
The second hidden lever: starting today vs starting "next year"
A 25× target is meaningless without contributions to compound. Per the Snowballr Cost-of-Waiting Index, at $500/mo and 8% returns, every year a 25-year-old delays reaching their FI number costs roughly $52,000 of final balance. By 35, the same 1-year delay still costs ~$40K. The math: starting one year earlier is functionally worth a 10% pay raise applied to your savings rate.
The 25× rule's limits
It assumes 30 years of retirement, no major lifestyle changes, no large unplanned expenses (long-term care averages $100K+/year for some), and that historical market patterns continue. It's a planning starting point, not a guarantee. Most realistic plans target 25× as a minimum and 30-33× as comfortable.
Withdrawal rate by retirement length
The 4% rule is calibrated for ~30-year retirements. Longer retirements (early retirees, FIRE) require lower withdrawal rates because portfolios face more bad-sequence years. Translates directly to the multiplier needed.
| Dimension | Retirement length | Suggested rate | Multiplier |
|---|---|---|---|
| 20 years (traditional retirement at 65) | ~5.0% | 20× expenses | |
| 25 years (typical retirement) | ~4.5% | 22× expenses | |
| 30 years (Trinity Study baseline) | ~4.0% | 25× expenses | |
| 35 years (early retirement at 60) | ~3.7% | 27× expenses | |
| 40 years (FIRE retirement at 50) | ~3.5% | 28-29× expenses | |
| 45 years (lean FIRE at 45) | ~3.3% | 30× expenses | |
| 50 years (FIRE at 40) | ~3.25% | 31× expenses |
How $50K of annual expenses compounds into the FI target
A 25× multiplier turns every dollar of recurring annual expense into 25 dollars of portfolio you must build. Cutting expenses is mathematically more powerful than earning more.
| Dimension | Annual spending | FI number at 25× | Years to FI at $30K/yr saving rate |
|---|---|---|---|
| $30,000/year | $750,000 | ~17 years | |
| $40,000/year | $1,000,000 | ~22 years | |
| $50,000/year | $1,250,000 | ~26 years | |
| $60,000/year | $1,500,000 | ~30 years | |
| $75,000/year | $1,875,000 | ~35 years | |
| $100,000/year | $2,500,000 | ~42 years |
Frequently asked questions
How do I count Social Security in the 25× calculation?
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Does the 4% rule work in retirement under 30 years long?
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How do I project when I'll hit my FI number?
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Plug in your own amounts with our free calculators.