The 4% Rule: Does It Still Work, and How Long Will Your Money Last Under It?

If you've read anything about retirement planning, you've run into the 4% rule. It shows up in magazines, podcasts, and forum threads, usually stated with a lot of confidence. Spend 4% of your savings in the first year, adjust for inflation after that, and your money should last about 30 years. Simple, memorable, and easy to repeat.

But is it still true? And what does it really tell you about how long your money will last? Let's take a closer look at where the rule came from, how it works, and where it holds up or falls short.

Where the 4% Rule Came From

The rule traces back to the early 1990s, when a financial planner named William Bengen set out to answer a practical question: how much could a retiree safely withdraw each year without running out of money? Rather than relying on average returns, he tested retirement start dates across decades of actual market history, including some ugly ones. He looked for the worst cases, such as people who retired right before a long stretch of poor returns and high inflation.

What he found was that a starting withdrawal of roughly 4%, raised each year with inflation, survived even those worst historical periods over 30 years. A few years later, a well-known study by three professors at Trinity University reached similar conclusions, and the idea spread widely. Over time, it got shortened to "the 4% rule."

How the Rule Actually Works

People often misunderstand the mechanics, so it's worth spelling out. You don't withdraw 4% of your balance every year. You calculate 4% of your balance once, at the start of retirement, and that becomes your first-year spending amount. After that, you simply raise the dollar amount each year to match inflation, regardless of what the market does.

Say you retire with $1,000,000. In year one, you take out $40,000. If inflation runs at 3%, year two's withdrawal is $41,200. Ten years in, you're taking about $53,800, and twenty years in, about $72,200. The balance may be rising or falling during that time, but the paycheck keeps pace with prices.

How Long Does Money Last Under the 4% Rule?

The rule was built around a 30-year retirement, but the answer to how long your money lasts depends heavily on the returns you earn. Here's what happens with a $1,000,000 portfolio under steady returns, with withdrawals rising 3% a year, for several starting withdrawal rates:

Two things stand out. First, at a 5% return, the 4% rule lasts about 36 years, a comfortable cushion beyond 30. Second, if returns come in closer to 3%, the same plan falls short of 30 years. That's why the rule isn't a promise. It's a guideline that works well when returns are decent and can struggle when they're not.

One caution: the table uses smooth, steady returns, which is not how the rule was originally tested. Bengen's work used real market sequences, with their ups and downs, which is a tougher test in some ways and a more realistic one in others.

Why People Question It Today

Over the past several years, the 4% rule has taken some heat. Here are the main reasons:

• Longer retirements. The rule was built for 30 years. If you retire at 55 and live into your nineties, you may need 35 to 40 years or more.
• Forward-looking returns. Some researchers argue that today's valuations and bond yields point to lower future returns than the past delivered. Morningstar's annual research, which uses projected returns rather than history, has recommended starting rates ranging from 3.3% in 2021 to 3.8% in 2022, and 3.9% for people retiring in 2026.
• A mostly U.S. sample. Historical U.S. markets have been among the strongest in the world, so some worry the results look better than a global average would.
• Taxes and fees. The original studies didn't account for either, and both can take a real bite.

On the other side, Bengen himself has since argued that his rule can be pushed higher, with his more recent work suggesting figures closer to 4.7% for some portfolios. The point is not that one camp is right. It's that careful people looking at the same question land in a range of roughly 3.3% to 4.7%, which tells you the rule is a starting point, not a law of nature.

What the 4% Rule Doesn't Capture

Real life is messier than any rule. A few things the 4% rule tends to gloss over:

• Spending isn't constant. Many retirees spend more in the early, active years and less in the middle years, then more again as healthcare costs rise later on.
• Other income. Social Security or a pension can cover a big part of your basics, which changes how much pressure falls on your portfolio.
• Flexibility. A rigid rule assumes you'll keep raising spending even after a market crash. Most real people would trim a bit, and that flexibility is worth a lot.
• Taxes. A $40,000 withdrawal from a traditional 401(k) isn't $40,000 of spending money once taxes are paid.
• Your own timeline. A 60-year-old and an 80-year-old need very different answers.

Using the 4% Rule Sensibly

Think of it as a quick way to size up a plan, not as a final answer. A simple sanity check works like this: multiply your annual spending need from savings by 25. If you need $40,000 a year from your portfolio, that suggests about $1,000,000. If you retire early or want extra safety, using 28 or 30 as the multiplier builds in more margin, which is the same as starting at roughly 3.5% or 3.3%.

From there, test your own situation. Enter your balance and your first-year withdrawal into a calculator, turn on inflation, and run a cautious return alongside a middle one. If your money lasts well past 30 years in the cautious case, you've probably got a solid plan. If it only lasts in the optimistic case, consider a lower starting rate, a bit of flexibility, or some extra years of saving.

Try It With Your Own Numbers

The 4% rule is a useful starting point, but your plan deserves more than a rule of thumb. The how long will my money last calculator on this site lets you try your own starting amount, withdrawal, and return assumptions in a couple of minutes, so you can see how the rule plays out for you. A few quick tests will tell you more than any headline can.

This article is for educational purposes only and is not financial, tax, or investment advice. Projections are estimates based on assumptions, and actual results will vary. Consider talking with a qualified financial professional about your specific situation.