The 4% Rule: How Much Can You Safely Withdraw in Retirement?
The 4% rule is a single percentage, drawn from three decades of market data, that still shapes how millions of people decide when they can afford to stop working.
The 4% rule: where the number comes from
So what exactly is the 4% rule, and where did it come from? It traces back to research by financial planner William Bengen in 1994. A group of professors at Trinity University later expanded his work in what people commonly call the Trinity Study. Bengen tested different withdrawal rates against historical U.S. market returns going back to the 1920s. He was looking for the highest rate a retiree could withdraw, adjusted for inflation each year after. The goal: don’t run out of money over a 30-year retirement, even in the worst historical periods tested.
4% was the rate that held up across those worst-case historical stretches, including retirements that began right before major market downturns. This isn’t a guarantee about the future. It draws its conclusion from how a specific set of historical scenarios actually played out, using the worst starting points found in the data rather than an average outcome across all of them.
How the math actually works
The rule says to withdraw 4% of your portfolio’s value in your first year of retirement. Then you adjust that dollar amount for inflation every year after, regardless of what the market does. On a $750,000 portfolio, 4% comes out to $30,000 in the first year, or $2,500 a month. If inflation runs 3% that year, the second year’s withdrawal becomes $30,900, and so on. It grows with inflation, rather than tracking the portfolio’s actual performance year to year.
This fixed, inflation-adjusted structure is deliberate: it provides a stable, predictable income stream, rather than one that swings with the market. That matters for anyone trying to budget household expenses in retirement the same way they did while working. In some years, the withdrawal amount can exceed the actual investment income the portfolio generated. That draws down principal, something the original research expected and accounted for, not a sign that anything has gone wrong.
Why 30 years specifically
The original research targeted a 30-year retirement horizon. That roughly matches a retirement starting somewhere in the mid-60s and lasting into the mid-90s. Someone retiring earlier, say, in their late 40s or 50s, is planning for a much longer retirement. It could easily stretch 40 years or more. That’s a materially different and harder problem than what the original 4% research aimed to answer. For an unusually long retirement horizon, planners generally consider a more conservative withdrawal rate prudent. That’s specifically because the original testing didn’t cover that longer duration of sustained withdrawals.
The debate over whether 4% still holds
The 4% rule has faced real scrutiny in recent decades. Critics point to today’s lower starting bond yields, compared to the historical periods the original research relied on. They also point to longer average life expectancies that stretch the required time horizon, and higher current market valuations. All of these factors could make a repeat of the historical worst-case scenarios less favorable going forward. Things looked different in the past.
Even Bengen himself has revised his own number over time. After further research incorporating a broader mix of asset classes, he revisited his own number. He later suggested a starting rate closer to 4.7% could still work safely. Other researchers have landed in a different place. Morningstar’s more recent analysis, for instance, has pointed toward a more conservative figure, closer to 3.7%, for someone retiring today. It cites higher current valuations and lower expected forward returns as the reason for the more cautious number. Reasonable, well-informed people land in different places on this question. That’s exactly why people still actively debate it, rather than treat it as settled. And it’s why the “right” number for you depends partly on which set of assumptions you find most convincing.
What the rule doesn’t account for
Bengen built the 4% rule around a simplified portfolio, typically a mix of U.S. stocks and bonds. It doesn’t factor in taxes, investment fees, or other income sources like Social Security or a pension. All of those affect how much you’d actually need to withdraw from a portfolio to cover real expenses. It also doesn’t account for major, uneven spending needs. Think a large healthcare expense arriving in a single year rather than spread evenly across retirement.
Sequence of returns risk is another real gap
Two retirees can have identical average returns over 30 years, and still end up in very different positions. Everything depends on timing: whether one experiences poor returns in the first few years of retirement, or the other experiences them later instead. Early losses on a shrinking, actively-withdrawn portfolio are harder to recover from than the same losses hitting later, since the portfolio has had less time to grow back. Financial planners call this sequence of returns risk, and it’s a big part of why the original research focused on worst-case historical starting points rather than simply averaging outcomes across all possible starting years.
One practical way retirees manage this risk is by keeping one or two years of planned withdrawals in cash, or a similarly stable holding, kept separate from the invested portfolio. This way, a market downturn early in retirement doesn’t force selling depressed investments to cover near-term living expenses.
Using the 4% rule as a planning starting point
Despite its limitations, the 4% rule remains genuinely useful as a first approximation. Dividing a target annual retirement income by 4% gives a rough portfolio size to aim for. $60,000 a year in desired income, for example, implies a target portfolio of roughly $1.5 million under this framework. That’s a starting number to refine, not a final answer, but it’s a far more concrete starting point than guessing.
People sometimes flip this same math around and call it the “rule of 25.” Dividing by 4% is mathematically identical to multiplying annual expenses by 25. Framed either way, the underlying message is the same: the number isn’t really about the withdrawal rate itself. It’s a shorthand for how large a portfolio needs to be, relative to spending, before retirement becomes realistically sustainable.
Estimate your own numbers
Our Retirement Calculator projects a retirement balance from your current savings and contributions. It then applies the 4% rule to estimate a sustainable monthly income from that balance. That gives you a concrete starting figure to plan around.
Common questions about the 4% rule
Financial planner William Bengen introduced the concept in a 1994 research paper. Finance professors at Trinity University later expanded and popularized it, in what people commonly call the Trinity Study.
Financial researchers genuinely debate this. Some argue current market conditions warrant a lower, more conservative starting rate. Others maintain 4% remains reasonable, especially when combined with flexible spending in years following weak market performance.
The underlying withdrawal math applies the same way regardless of account type. But 401(k)s and traditional IRAs come with required minimum distributions starting at a certain age. Those can force withdrawals that don’t perfectly align with a strict 4% schedule.
This is the core risk the 4% rule specifically aimed to survive. The original research included historical retirements that began right before major downturns. Even so, many retirees choose to build in flexibility. They spend somewhat less in years immediately following a market decline. That acts as an added safety margin beyond the rule’s baseline assumption.
Divide your desired annual retirement income by 4%, or equivalently multiply by 25. Someone wanting $60,000 a year in retirement income would target a portfolio of roughly $1.5 million under this framework.
Sequence of returns risk means two retirees with identical average returns can end up in very different positions. It depends on whether poor returns hit early or late in retirement. Early losses on a withdrawn-from portfolio are harder to recover from.
No. The basic 4% rule builds around portfolio withdrawals alone and doesn’t factor in Social Security, pensions, or other income sources. Those sources would reduce how much you actually need to withdraw from savings.
The rule of 25 is mathematically identical to the 4% rule: multiply your annual expenses by 25 to estimate the portfolio size needed to sustain that spending using a 4% withdrawal rate.
Many early retirees use a more conservative rate, since the original 4% research targeted a 30-year retirement horizon. An early retirement can easily stretch 40 years or more.