What is the 4% rule?
The 4% rule is a retirement guideline: withdraw 4% of your portfolio in your first year, then adjust that dollar amount for inflation each year afterward. Historically, a portfolio built that way lasted about 30 years. It is the basis for the Rule of 25, which says you need roughly 25 times your annual spending saved. It is a helpful baseline, not a guarantee.
How the rule works in practice
Say you retire with $1,000,000. In year one you withdraw 4%, or $40,000. In year two you do not take 4% again; you take last year's $40,000 plus inflation. You keep raising the dollar amount with inflation each year regardless of what the market does. The idea is a steady, predictable paycheck from a portfolio of stocks and bonds.
Where the 4% number comes from
The rule grew out of research testing how much a retiree could withdraw without running out over a 30-year retirement, using historical U.S. market returns. Four percent was the rate that survived even the worst starting years in the data. The key phrase is 30 years: the rule was calibrated to that horizon, not to a 45- or 55-year retirement.
The limitations
The 4% rule assumes a fixed spending pattern, a specific stock and bond mix, and a roughly 30-year window. It also assumes you keep spending on schedule through market crashes. Its biggest blind spot is sequence risk: a bad market in your first few years can permanently damage a portfolio, even if long-run average returns are fine.
The 4% rule in 2026: what the latest research says
The number is no longer settled at exactly 4%. William Bengen, who first defined the rule in 1994, raised his own safe starting rate to about 4.7% in his 2024–2025 work after adding more asset classes and a longer data set. Others moved the opposite way: Morningstar's 2024–2025 analysis put the safe rate near 3.7%, and Vanguard's guidance sits around 3.5% to 4.5% depending on your stock and bond mix. Taken together, most current research clusters the safe withdrawal rate for a 30-year retirement between roughly 3.7% and 4.2%.
The spread itself is the lesson. Reasonable experts disagree by a full percentage point because the answer depends on assumptions no rule can fix for you — your time horizon, your allocation, current valuations, and how flexible your spending is. For a longer horizon the safe rate falls further: published extensions put it closer to 3.25% to 3.5% for a 50-year retirement. Rather than pick one number from the debate, it is more useful to test your own withdrawal rate against thousands of market paths and read the probability directly.
What to use instead of a single rate
Rather than committing to one fixed rate, many planners test a range of withdrawal rates against thousands of possible market paths and look at the probability the money lasts. That approach can reveal that 3.5% is safer for someone retiring young, while 4.5% may be workable for someone with substantial guaranteed income like Social Security. Your safe rate is personal.
Turn the rule into your odds
The 4% rule gives you a starting point; a simulation gives you a probability. By running your own savings, spending, and timeline through many market scenarios, you can see how often your plan succeeds and adjust your withdrawal rate until the odds look comfortable.