Coast FIRE: The Strategy That Lets You Stop Saving for Retirement
Coast FIRE is the point where an existing retirement portfolio may grow to a target without further contributions, based on the return and inflation assumptions used.
The 4% Rule: What It Is, How It Works, and Its Limitations
The 4% rule is a historical US retirement-withdrawal framework, not a guarantee. Learn its original assumptions, how to model it, and why early retirement requires stress testing.
What is the 4% rule?
The 4% rule is a widely used starting framework for estimating retirement withdrawals from an investment portfolio.
The rule states: withdraw 4% of your starting portfolio in year one of retirement, then adjust that dollar amount annually for inflation. Historical US simulations found that this approach often supported 30-year periods, but it does not guarantee that a portfolio will last.
For FIRE planning, the 4% rule converts directly into the 25x formula: if you need $50,000/year, you need $1,250,000 invested ($50,000 ÷ 0.04 = $1,250,000). Multiply annual expenses by 25 to get your FIRE number.
It is simple and grounded in historical research, but early retirees and people outside the United States should understand its limitations.
The Trinity Study: the research behind the rule
The 4% rule is closely associated with the Trinity Study, published in 1998 by finance professors Philip Cooley, Carl Hubbard, and Daniel Walz at Trinity University.
Their methodology: analyze historical US market data from 1926 to 1995, test every 30-year rolling period, and calculate what percentage of portfolios at various withdrawal rates survived the full 30 years.
Results for a 50% stocks / 50% bonds portfolio:
| Withdrawal Rate | 30-Year Success Rate |
|---|---|
| 3% | 100% |
| 4% | 98% |
| 5% | 80% |
| 6% | 68% |
| 7% | 52% |
| 8% | 36% |
For a 75% stocks / 25% bonds portfolio, the table in the original paper also reported a 98% historical success rate over 30 years.
These figures describe specific historical US stock-and-bond portfolios, expense assumptions, and periods. They are not forecasts for future US returns or evidence that the same rate works in every country, asset allocation, tax system, or fee environment.
How to apply the 4% rule step by step
Applying the rule is straightforward:
Step 1: Determine your annual retirement expenses. Be thorough — include housing, food, transportation, healthcare, travel, insurance, and any debt payments.
Step 2: Divide annual expenses by 0.04 (or multiply by 25) to get your portfolio target. - $40,000/year → $1,000,000 - $60,000/year → $1,500,000 - $80,000/year → $2,000,000
Step 3: In your first year of retirement, withdraw 4% of your starting portfolio.
Step 4: Each subsequent year, increase your withdrawal by the inflation rate.
Example — applying the 4% rule over 5 years: - Starting portfolio: $1,250,000 - Year 1 withdrawal: $50,000 (4%) - Year 2 (3% inflation): $51,500 - Year 3: $53,045 - Year 4: $54,636 - Year 5: $56,275
Your withdrawals increase with inflation, maintaining your purchasing power. The portfolio continues to grow (in good market years) or draws down more slowly (in bad years).
Model your assumptions with our 4% Rule Calculator →
The 4% rule for early retirement: why it doesn't fully apply
The original Trinity Study tables focused heavily on retirement periods of up to 30 years.
If you retire at 35, 40, or 45, the portfolio may need to support spending for 50 years or longer. A 30-year historical result cannot establish a safe rate for that longer horizon.
Some early-retirement plans therefore test lower initial rates, such as 3-3.5%, alongside 4%: - 3.5% rate → multiply annual expenses by 28.6 - 3% rate → multiply annual expenses by 33.3
The tradeoff is a larger required portfolio and a lower initial withdrawal. Whether that margin is sufficient still depends on future returns, inflation, fees, taxes, allocation, spending flexibility, and retirement length.
Withdrawal rate comparison: what each rate means in practice
| Withdrawal Rate | FIRE Multiplier | Portfolio for $50k/yr | Portfolio for $70k/yr |
|---|---|---|---|
| 5% | 20x | $1,000,000 | $1,400,000 |
| 4.5% | 22x | $1,111,000 | $1,556,000 |
| 4% | 25x | $1,250,000 | $1,750,000 |
| 3.5% | 28.6x | $1,429,000 | $2,000,000 |
| 3% | 33.3x | $1,667,000 | $2,333,000 |
| 2.5% | 40x | $2,000,000 | $2,800,000 |
The difference between 4% and 3% requires a portfolio that's about 33% larger for the same initial spending level. That is a significant tradeoff between saving longer and beginning with a lower withdrawal rate.
Criticisms of the 4% rule and what they miss
The 4% rule has attracted criticism, especially in low-yield market environments. Understanding these criticisms — and their limitations — helps you make better decisions.
Criticism 1: "Current valuations make future returns lower" This argument: because current stock valuations (price-to-earnings ratios) are elevated compared to historical averages, future returns will be lower, making the 4% rule too aggressive.
Planning implication: Future returns are unknowable. Test multiple return, inflation, and withdrawal assumptions rather than treating a single rate as safe under all valuations.
Criticism 2: "The rule ignores sequence of returns risk" This is valid. A major market decline in years 1-5 of retirement is far more damaging than the same decline later, because you're withdrawing at depressed prices.
Planning implication: Historical rolling-period tests include difficult starting dates, but they cannot capture every future sequence. A cash reserve and flexible spending can reduce the need to sell during a decline, although neither removes sequence risk.
Criticism 3: "The rule uses US market data and ignores global portfolios" True — the US stock market has had exceptional returns historically. Other developed markets have had lower long-term returns.
Planning implication: Global diversification spreads market exposure, but it does not guarantee higher returns or make a particular withdrawal rate sustainable. Test assumptions appropriate to your own investments, currency, fees, taxes, and jurisdiction.
Criticism 4: "Nobody actually spends a fixed inflation-adjusted amount" Also true — real retirees naturally spend less in bad market years and more in good ones.
Planning implication: Reducing discretionary spending after poor returns can lower withdrawals. The benefit depends on how much spending is truly flexible and how quickly changes are made.
Strategies to make the 4% rule more robust
The cash buffer strategy
Keep 1-2 years of expenses in cash or short-term bonds outside your investment portfolio. During market downturns, spend from the cash buffer rather than selling investments at depressed prices. Replenish the buffer when markets recover.
This may reduce forced selling during a shorter downturn, but a reserve can be exhausted and does not eliminate sequence-of-returns risk.
The flexible spending strategy
Instead of fixed inflation-adjusted withdrawals, allow spending to fluctuate with portfolio performance. A simple rule: if your portfolio falls below your starting value, reduce spending by 10%. If it exceeds your starting value by 20%, allow spending to increase.
Flexibility can improve outcomes in many simulations, but it does not make a 4.5-5% initial rate equivalent to a fixed 3.5% rate in every scenario. Model the specific spending rule and minimum acceptable budget before relying on it.
The "one more year" buffer
Work one additional year beyond your calculated FIRE date. This accomplishes three things: adds more savings, reduces the retirement period by one year, and provides psychological confidence.
Supplemental income in early retirement
Maintaining even small supplemental income in early retirement dramatically reduces portfolio withdrawal pressure. $15,000/year from part-time consulting, rental income, or a passion project reduces a $60,000 spending need to $45,000 — lowering the FIRE number by $375,000 at a 4% withdrawal rate.
What rate should you actually use?
The ranges below are scenarios to test, not universal recommendations:
A 4% scenario may be relevant if: - You're retiring at 60+ with a 30-year horizon - You have flexibility to reduce spending in bad markets - You have supplemental income sources (Social Security, pension, part-time work) - You're comfortable with a small probability of portfolio depletion
A 3.5% scenario may be worth testing if: - You're retiring in your 40s-50s (30-40 year horizon) - You want a meaningful safety margin - Your spending is relatively fixed without flexibility
A 3% scenario may be worth testing if: - You're retiring in your 30s or younger (40-50+ year horizon) - Your spending has limited flexibility - You want a lower starting withdrawal, while recognizing that no rate provides certainty
A higher-rate scenario should be stress-tested carefully if: - You have significant guaranteed income (Social Security, pension) - You have additional assets you already control; do not rely on an uncertain inheritance - You have flexible spending and would cut dramatically if needed - Your portfolio is primarily in annuities or other guaranteed instruments
The bottom line on the 4% rule
The 4% rule is not perfect — no planning tool is. But it is well-researched, historically validated, and provides a useful starting framework for retirement planning.
For early retirees, test lower rates such as 3-3.5% as well as 4%, especially for horizons beyond the 30 years emphasized in the original study.
Cash reserves, flexible spending, and reliable supplemental income can make a plan more resilient. The 4% rule remains a useful illustration, not a complete determination of retirement readiness.
Frequently asked questions
What happens if my portfolio runs out of money under the 4% rule? A failed historical simulation means the modeled portfolio was depleted before the end of the period. Do not assume a late-stage shortfall would be easy to solve; monitor the plan and adjust spending or income early when possible.
Should I include Social Security in my 4% rule calculation? Account for US Social Security only from the age you expect benefits to begin. Before that date, the portfolio must cover the full spending gap. Use your personal estimate and test changes in claiming age, taxes, and benefit assumptions rather than subtracting a future benefit from every retirement year.
Does the 4% rule work for Roth IRA accounts? The withdrawal framework can be modeled across account types, but taxes, access rules, and withdrawal ordering affect spendable income. In the United States, qualified Roth IRA distributions are generally tax-free; other accounts and jurisdictions have different rules.
What is the "4% rule" called in financial planning? It's formally called the "safe withdrawal rate" (SWR) or "sustainable withdrawal rate." The 4% figure is the most commonly cited safe withdrawal rate for 30-year retirement periods based on historical US market data.
Can I use the 4% rule if I have a variable income in retirement? Yes — this actually works in your favor. Variable income (freelancing, part-time work, rental income) reduces how much you need to withdraw from your portfolio, effectively making your actual withdrawal rate lower than 4% in years when outside income is available.