The 4% Rule: How Long Will Your Retirement Savings Last?

The 4% rule is one of the most cited — and most debated — concepts in retirement planning. It gives you a simple way to estimate how much you can safely spend each year without outliving your money. Here is everything you need to know about where it came from, how it works, and when to adjust it.

Origin: William Bengen's Research, Later Confirmed by the Trinity Study

The 4% rule originates with financial advisor William Bengen, who published "Determining Withdrawal Rates Using Historical Data" in the Journal of Financial Planning in 1994. Using historical U.S. stock and bond returns, Bengen found that a retiree withdrawing 4% of their portfolio in year one, then adjusting that dollar amount for inflation each year after, could expect a 30-year portfolio to survive nearly every rolling historical period he tested.

Four years later, in 1998, three finance professors at Trinity University — Philip Cooley, Carl Hubbard, and Daniel Walz — published a related but independent study analyzing historical stock and bond returns across a range of portfolio allocations and withdrawal rates. Their conclusion reinforced Bengen's: a portfolio made up of roughly 50–75% stocks and the rest in bonds could sustain a 4% withdrawal rate (adjusted annually for inflation) with approximately 95% success across the 30-year periods studied. This second, broader study is what popularized the term "safe withdrawal rate" in the financial-planning industry — but the 4% figure itself, and the rule's core logic, trace back to Bengen four years earlier.

How the 4% Rule Works in Practice

The rule is simple to apply. In your first year of retirement, you withdraw 4% of your portfolio's total value. Each subsequent year, you adjust that dollar amount for inflation — not 4% of the new balance, but 4% of the original balance plus inflation adjustments.

Example: You retire with $1,000,000.

• Year 1: Withdraw $40,000 (4% of $1M)
• Year 2 (3% inflation): Withdraw $41,200
• Year 3: Withdraw $42,436

The remaining portfolio stays invested and — historically — has continued to grow even as withdrawals are made.

Withdrawal Rate Comparison Table

Different withdrawal rates produce dramatically different monthly income and carry different sustainability profiles. Here is how they compare for a $1,000,000 portfolio:

Sequence of Returns Risk

One of the most important — and least intuitive — concepts in retirement planning is sequence of returns risk. It describes the danger that the order in which investment returns occur matters as much as the average return itself.

Consider two retirees who both earn a 7% average annual return over 20 years. One experiences strong returns in early retirement followed by poor returns late. The other faces poor returns first, then strong ones. The retiree who faces early losses while withdrawing funds will end up with far less money — even though the average return is identical.

Why? Because withdrawals during a down market force you to sell shares at depressed prices, permanently reducing the number of shares left to recover when the market rebounds.

When to Adjust Your Withdrawal Rate

The 4% rule is a starting framework, not a rigid command. There are several situations where adjusting your withdrawal rate makes sense:

Retire Earlier Than 65

Both Bengen's original research and the Trinity Study modeled 30-year retirements. If you retire at 50 or 55, your money needs to last 40–50 years. A 3% to 3.5% withdrawal rate is a more appropriate target for long-horizon retirements.

Markets Drop Early in Your Retirement

If a bear market strikes in your first few years of retirement, consider temporarily cutting withdrawals by 10–20%. Even a small reduction in spending during bad years significantly improves long-term outcomes. This is sometimes called a "guardrails" strategy.

You Have Other Income Sources

Social Security, a pension, rental income, or part-time work all reduce how much you need to draw from your portfolio. If you have guaranteed income streams covering a significant portion of expenses, your portfolio withdrawal rate can be more flexible — potentially even higher than 4% for discretionary spending.

Interest Rates Are Low

Both Bengen's research and the Trinity Study assumed a mix of stocks and bonds earning historical rates. In prolonged low-yield environments, bond returns may lag historical averages, slightly reducing the effectiveness of a balanced portfolio. Some advisors recommend a 3.3% to 3.7% rate in these conditions.

The Bottom Line

The 4% rule is a powerful, research-backed starting point for building a retirement withdrawal strategy. It tells you roughly how much you can spend each year while maintaining a high probability of not outliving your savings. But it is not a guarantee — sequence of returns risk, healthcare costs, and changing markets mean flexibility is essential.

Combine the 4% rule with a realistic budget, a cash reserve for early retirement emergencies, and a willingness to adjust spending in bad market years, and you will have a plan that can weather most scenarios.

This article is for educational purposes only and does not constitute financial advice. Consult a licensed financial advisor before making retirement decisions.