What is the 4% rule for retirement?

The 4% rule states that retirees can withdraw 4% of their portfolio in the first year of retirement, then adjust that amount for inflation each year, with a high probability of never running out of money over a 30-year period. It originates from William Bengen's 1994 research in the Journal of Financial Planning, which found the maximum safe starting rate was 4.15% — rounded to 4% as a practical rule.

Is the 4% rule safe for early retirement?

Not automatically. Bengen's original research covered 30-year retirement horizons. If you retire at 50, your horizon is 40+ years — a full decade longer. The research consensus for 40-year horizons is approximately 3.5%, and for 50-year horizons approximately 3.0%. Morningstar's 2026 annual withdrawal rate report sets the safe rate at 3.9% for a 30-year retirement. For longer early-retirement horizons, 3.0–3.5% is the appropriate ceiling.

What did the Trinity Study find about the 4% rule?

The Trinity Study (Cooley, Hubbard, and Walz, 1998) extended Bengen's research with a portfolio success-rate table across different stock/bond allocations and withdrawal rates. For a 30-year period with a 75% stock / 25% bond portfolio, a 4% withdrawal rate had a 95–98% historical success rate. At 5%, success dropped to 80% for the same horizon. The Trinity Study is the source of the widely-cited success-rate tables in retirement planning.

The 4% Rule: Origin, Research, and What Early Retirees Need to Know

The 4% rule is the most widely cited number in retirement planning. It says you can withdraw 4% of your portfolio in year one, adjust for inflation each year after, and have a high probability of never running out of money. But where did that number come from, is it still valid, and — most importantly — does it apply to a 40-year early retirement?

Where the 4% rule came from: William Bengen (1994)

The 4% rule traces to a single paper: William Bengen's "Determining Withdrawal Rates Using Historical Data," published in the Journal of Financial Planning in October 1994.¹

Bengen's question was simple: what is the highest fixed, inflation-adjusted withdrawal rate that — applied to any 30-year historical period from 1926 through 1992 — would never have depleted a portfolio? He tested a 50% large-cap U.S. stock / 50% intermediate-term U.S. government bond allocation and found the answer was 4.15%, rounded to 4% as a practical rule.

The 4.15% is sometimes called the SAFEMAX — the maximum withdrawal rate that survived every historical 30-year window, including the worst starting years (1937, 1965, 1966). It is not an average or a median; it is the worst-case-survivable rate.

Key assumption: 30-year horizon. Bengen's research was designed to answer the question for a retiree leaving a job at 65. The 4% figure was never tested against or intended for 40- or 50-year retirements.

Bengen later extended his research to include small-cap equities. With a three-way split of large-cap stocks, small-cap stocks, and bonds, the SAFEMAX rose to approximately 4.7% — the so-called "SAFEMAX with asset diversification."¹

The Trinity Study (1998)

Four years later, professors Philip Cooley, Carl Hubbard, and Daniel Walz published "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable" (1998).² The Trinity Study became the second foundational paper in withdrawal-rate research.

Their approach was different: rather than finding the worst-case-survivable rate, they built success-rate tables showing what percentage of historical 30-year periods a given rate survived at different stock/bond allocations.

Key finding for a 75% stock / 25% bond portfolio:

Withdrawal Rate	30-Year Success Rate (75/25)
3%	100%
4%	95–98%
5%	~80%
6%	~67%

The 95%+ success at 4% for 30 years became the most-cited retirement planning benchmark in existence.

What Morningstar says in 2026

Morningstar publishes an annual withdrawal rate report. For 2026, they recommend a starting withdrawal rate of 3.9% for a 30-year retirement with a 30–50% equity allocation (90% probability of success).³ This is up from 3.7% in their 2024 report, primarily due to improved return assumptions across asset classes.

The 3.9% figure is for a standard 30-year retirement. Morningstar notes that flexible spending strategies — like the Guyton-Klinger guardrails or delaying Social Security — can support starting rates as high as 5.7%.

Why the 4% rule breaks down for early retirement

Three structural reasons the 4% rule doesn't automatically apply when you retire in your 40s or 50s:

1. The horizon is longer

At 4%, a 30-year retirement has roughly 95–98% historical success. But the same 4% applied to a 50-year horizon drops to approximately 80% success in historical data — meaning 1 in 5 early retirees runs out of money before the end. The extra 20 years give bad sequences more time to compound and give portfolios fewer years to recover.

2. Sequence of returns risk is more severe

The order of returns — not the average — determines whether a portfolio survives early in retirement. A 30% market drop in year 3 of a 30-year retirement is less damaging than the same drop in year 3 of a 50-year retirement, because the 50-year plan depends on recovery compounding for longer. See: sequence of returns risk guide.

3. Healthcare before Medicare is a real cost

Retiring at 52 means 13 years of healthcare expense before Medicare. Unsubsidized silver plan premiums for a 60-year-old can exceed $15,000/year — a cost the original retirement research didn't model. Early retirees need to budget healthcare separately and coordinate ACA income to stay below the subsidy cliff. See: healthcare before 65 guide.

Horizon-adjusted withdrawal rates for early retirement

These rates reflect the research consensus (Bengen, Blanchett, Pfau, Big ERN) on historically supported withdrawal rates by retirement horizon.⁴ They are consistent with the safe withdrawal rate calculator on this site:

Retirement Age	Horizon	Supported Rate	FI Multiplier
60–65	30 years	4.0%	25×
55–59	35 years	3.75%	26.7×
50–54	40 years	3.5%	28.6×
45–49	45 years	3.25%	30.8×
35–44	50 years	3.0%	33×
Below 35	55 years	2.75%	36.4×

Is the 4% rule too conservative — or not conservative enough?

The debate runs in both directions:

The optimistic case: Michael Kitces has argued that 4% is actually quite safe even in today's environment because bond yields have risen since the low-rate era that drove Morningstar's earlier 3.3% recommendation. Starting from higher yields, bonds contribute more to real returns. Bengen himself has said 4.7% is justifiable with a well-diversified multi-asset portfolio.

The pessimistic case: Big ERN (Karsten Jeske) argues that current equity valuations — as measured by the Shiller CAPE ratio — predict below-average forward returns. His framework ties the safe withdrawal rate to CAPE: when CAPE is above 20 (it was near 38 in early 2026), he recommends 3.25–3.5% for early retirees even for 40-year horizons.⁴

The practical middle: Most early retirement planners treat 3.25–3.5% as their planning floor for 40-year horizons, use conservative rates for the initial withdrawal, and keep flexible levers in reserve — part-time income, spending cuts, or dynamic withdrawal rules — as the real safety margin.

How dynamic withdrawal rules change the math

The static 4% rule assumes you withdraw 4% × inflation every year regardless of portfolio performance. That rigidity is what makes it break at higher rates. Dynamic strategies allow you to start higher because you agree to cut spending when the portfolio drops and raise it when it surges.

Guyton-Klinger guardrails: Start at ~5% for a 40-year retirement. Cut 10% if portfolio drops too far; raise 10% if it's well ahead. This converts the binary pass/fail of the static rule into a managed range. See: Guyton-Klinger calculator.
Variable Percentage Withdrawal (VPW): Recalculate withdrawal each year as a percentage of the current portfolio using the PMT formula. Cannot fail — but spending fluctuates with markets. See: VPW calculator.
Floor + upside: Lock a fixed income floor (Social Security, TIPS ladder, small SPIA) and take discretionary spending from the remaining portfolio. Even a bad sequence only affects the upside spending.

4 practical steps for early retirees

Use the horizon-appropriate rate from the table above, not 4%, as your planning baseline.
Stress-test with a Monte Carlo simulator. The historical success rates are based on one country's data (US). Monte Carlo draws from a distribution of outcomes. Your plan should hold at 90%+ success before you feel confident. See: Monte Carlo simulator.
Identify your flexible levers now. What would you cut first? Can you generate $10,000–$20,000/year in part-time income in a bad sequence year? These options are worth more than a lower withdrawal rate in many scenarios.
Coordinate the ACA cliff. At 3.5%, a $2M portfolio generates $70,000/year. A single filer at $70,000 MAGI is above the ACA subsidy cliff ($63,840 in 2026). Income management to stay below the cliff can be worth $10,000–$15,000/year in healthcare subsidies.

The 4% rule is a starting point, not a plan. It tells you whether your portfolio is in the right ballpark. Translating it into a 40-year plan requires healthcare coordination, tax sequencing, sequence-of-returns mitigation, and Social Security timing — areas where a fee-only early retirement specialist earns their fee many times over.

Bengen, W.P. (1994). "Determining Withdrawal Rates Using Historical Data." Journal of Financial Planning, October 1994. FPA: Revisiting Bengen's SAFEMAX (2023).
Cooley, P.L., Hubbard, C.M., & Walz, D.T. (1998). "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable." AAII Journal. Updated 2011 in AAII Journal with extended data.
Morningstar. "What's a Safe Retirement Withdrawal Rate for 2026?" Morningstar, 2026. 3.9% for 30-year horizon, 90% confidence, 30–50% equity allocation.
Jeske, K. (Early Retirement Now). The Safe Withdrawal Rate Series. Recommends 3.25–3.5% for 40-year FIRE horizons with current CAPE valuations.
Pfau, W. (RetirementResearcher.com). "Safe Withdrawal Rates for Retirement and the Trinity Study." Overview of the research history with updated data through 2023.

Values verified as of August 2026. Tax thresholds (ACA cliff) from HHS 2026 FPL tables.