Compare smooth, cautious and weak-early-return scenarios using your own portfolio, inflation, return and retirement-horizon assumptions.
The 4% rule is a historical retirement-withdrawal rule of thumb, not a promise that 4% is always safe. In its classic form, the retiree withdraws about 4% of the starting portfolio in year one, then adjusts the withdrawal amount for inflation—not 4% of the current portfolio every year.
What the rule means
The classic rule starts with a first-year withdrawal of about 4% of the initial retirement portfolio and then adjusts the withdrawal amount over time for inflation. It became widely known from historical U.S. retirement research, including William Bengen's 1994 work.
Why 25x is only a shortcut
The original research was based on historical U.S. market and inflation data and specific portfolio assumptions. A real plan can differ by country, asset allocation, taxes, fees, retirement length, inflation, pension income and spending flexibility.
Retirement length changes the question
A rate that appeared durable across many 30-year historical periods does not automatically answer a 40- or 50-year early-retirement problem. A longer horizon creates more years of withdrawals, inflation exposure and market uncertainty.
Sequence-of-returns risk is one reason the same rate can behave differently
Poor returns early in retirement can cause more damage than the same losses arriving later because withdrawals are reducing the portfolio at the same time. NISM specifically highlights sequence risk alongside longevity and inflation risk.
How Carrowmont uses withdrawal-rate assumptions
Carrowmont treats the withdrawal rate as a user-controlled planning assumption. It should be tested alongside a spending level, inflation, return assumptions and the age through which the plan is expected to last. A lower rate generally implies a larger target; a higher rate implies a smaller target but places more demand on the portfolio.
Where the rule came from
William Bengen’s 1994 historical research tested retirement withdrawals across difficult US market periods. On his own site, Bengen explains that his original finding was 4.15% for the initial withdrawal under the historical assumptions he studied, with later withdrawals adjusted for inflation. The public shorthand became the “4% rule.”
The mechanics are often misunderstood
Why 25× annual spending appears in FI discussions
1 ÷ 0.04 = 25If the first-year portfolio withdrawal is 4% of assets, the starting portfolio is 25 times that first-year withdrawal. This is arithmetic, not proof that the portfolio will last.Modern research does not produce one permanent number
Morningstar’s 2026 US retirement-income discussion cites a 3.9% starting rate in its base case for a 30-year horizon with a 90% probability-of-success target and inflation-adjusted spending. The number changes with asset allocation, valuation assumptions, inflation, horizon and spending flexibility. For early retirement, its September 2026 analysis shows lower starting rates as the horizon lengthens.
| Planning horizon | Illustrative Morningstar 2026 research context | Why it changes |
|---|---|---|
| 30 years | 3.9% base-case starting rate in cited US research | Portfolio must support three decades of inflation-adjusted spending |
| 35 years | About 3.5% in cited early-retirement analysis | More years and more opportunities for adverse sequences |
| 40 years | About 3.3% in cited analysis | Longer liability requires more initial margin |
| 50 years | About 2.9% in cited analysis | Very long horizon increases longevity and sequence exposure |
They are outputs of a particular research model, asset mix, market assumptions and success criterion. They are useful context for understanding horizon sensitivity—not a personal withdrawal recommendation.
Spending flexibility changes the problem
A retiree who insists on raising every withdrawal by inflation regardless of markets has a different risk profile from someone who can defer travel, gifting or large purchases after a weak year. Dynamic-spending and guardrail approaches can support higher initial spending in some simulations, but they exchange portfolio safety for more variable lifestyle spending.
Taxes, fees and non-portfolio income matter
A withdrawal rate describes money leaving a portfolio. It does not automatically equal spendable after-tax income. Account taxes, advisory/fund fees and transaction costs can raise the gross withdrawal needed. Conversely, pensions and other reliable income can reduce the amount the portfolio must fund.
Use the rule as a stress-test anchor
- Estimate portfolio-funded first-year spending.
- Calculate what 3%, 3.5%, 4% and 5% imply for starting portfolio size.
- Test at least one poor early-return sequence and one high-inflation sequence.
- Identify spending that can flex if the current withdrawal rate becomes uncomfortable.
- Review the plan as the remaining horizon and portfolio value change.
Historical worst cases and forward-looking models answer different questions
Bengen’s original work asks how a fixed real withdrawal would have survived historical US return and inflation sequences. Forward-looking models such as Morningstar’s use assumptions about future asset returns, inflation and correlations and test many simulated paths. Neither framework can guarantee the future; agreement and disagreement between them are information about model sensitivity.
A “safe” rate always contains a success definition
A 90% probability of assets remaining after 30 years is different from a 100% historical survival test, and both are different from preserving inflation-adjusted principal. Before comparing two withdrawal-rate studies, check the horizon, asset allocation, fees, taxes, inflation treatment and definition of failure.
The rule is a starting-spending framework, not portfolio management
It says little about rebalancing, account withdrawal order, tax management, cash reserves, healthcare or late-life spending. Those decisions can matter as much as the initial percentage. The rule is valuable because it frames the spending-versus-capital trade-off, not because it solves retirement by itself.
Worked example: The rule starts with the opening portfolio, not each year's balance
Suppose a retirement portfolio starts at 10,000,000. A 4% initial withdrawal would be 400,000 in year one. If inflation were 5%, the classic rule would increase the year-two withdrawal to about 420,000—it would not simply recalculate 4% of whatever the portfolio happens to be worth in year two.
| Year | Illustrative withdrawal | How it was set |
|---|---|---|
| 1 | 400,000 | 4% of the starting portfolio |
| 2 | 420,000 | Prior withdrawal increased by the assumed 5% inflation |
The familiar 25× spending shortcut is the reciprocal of 4%: Annual spending ÷ 0.04. It is a convenient starting relationship, not proof that a portfolio will support every retirement length, asset mix or market path.
Checklist: Questions to ask before using a 4% assumption
- How long might the retirement need to last?
- What asset mix and fees are assumed?
- Are taxes included in the spending number?
- How much spending can change after a weak market?
- What other dependable income reduces portfolio withdrawals?
- How would higher inflation or poor early returns affect the plan?
- Have you tested more than one withdrawal rate rather than treating 4% as a promise?
The rule was developed from historical U.S. market research. Use the 4% Rule Stress Test to compare different assumptions, and the Withdrawal / Drawdown Calculator for a broader withdrawal-path illustration.
Frequently asked questions
Does the 4% rule mean withdraw 4% of the current balance every year?
No. The classic interpretation uses a percentage of the starting portfolio for year one, then adjusts the withdrawal amount for inflation. A fixed percentage of current assets is a different strategy.
Is 4% guaranteed to last 30 years?
No. Historical and model-based research depends on asset allocation, market sequence, inflation, fees, taxes and assumptions. Future outcomes can differ.
Should an early retiree use the same rate?
A longer horizon generally requires more margin. Recent Morningstar research cited here illustrates lower model-based starting rates for 35-, 40- and 50-year horizons.
Can I spend more if I am willing to cut spending after market declines?
Flexible strategies can support different starting rates in research, but the trade-off is variable annual spending. The plan should identify which expenses are genuinely flexible.
Sources and how this guide was prepared
This Carrowmont guide was drafted with AI assistance, then structured and checked against the cited external sources and Carrowmont calculation conventions. Worked examples are illustrative, use simplified assumptions, and are not forecasts or individualized recommendations.