The 4% rule: where it came from and where it breaks

By Tom, CPA · Updated October 25, 2026

TL;DR: The 4% rule says that, in historical U.S. data, withdrawing 4% of a portfolio in the first year of retirement and then adjusting that dollar amount for inflation lasted at least 30 years. It's a useful starting point. Early retirees face longer horizons, different portfolios and taxes, so treat 4% as a planning anchor rather than a promise.

Educational only, not tax, legal, or investment advice. Examples are illustrations, not predictions. Rules and limits change; verify current figures and talk to a qualified professional about your situation.

Almost every FIRE plan starts with the same shortcut: multiply your annual spending by 25 and that's your number. The shortcut comes from the “4% rule.” It's one of the most useful ideas in personal finance and one of the most misunderstood. This guide explains what it actually says, what it doesn't, and how to use it sensibly when your retirement might last 40 or 50 years.

Think of the 4% rule as a sturdy old bridge built by careful engineers in the 1990s. Captain Compound walks across it every day. But it was load-tested for 30-year trips, and some FIRE folks are planning to drive a 50-year moving truck over it. Let's inspect the bolts.

CPA Warning Label: The 4% rule is a historical observation, not a pinky promise from the universe. Keep away from overconfidence. Do not tattoo on body.

What the rule actually says

The rule describes a specific withdrawal method:

1. In the first year of retirement, withdraw 4% of your starting portfolio.
2. In each later year, withdraw the same dollar amount, increased by inflation, regardless of what the market did.

Illustration: with a $1,000,000 portfolio you'd withdraw $40,000 in year one. If inflation were 3% that year, you'd withdraw $41,200 in year two, and so on. Your withdrawals don't drop when markets fall, and they don't jump when markets boom.

That's different from withdrawing 4% of whatever the balance happens to be each year. That second approach can never run out of money, but your income would swing with the market.

Where it came from

In 1994 financial planner William Bengen published research in the Journal of Financial Planning testing historical U.S. stock and bond returns going back to the 1920s. He asked: what's the highest starting withdrawal rate, adjusted for inflation each year, that would have lasted at least 30 years in every historical starting year? For portfolios with a large stock allocation, the answer was a little above 4%. The worst outcomes came from retirements that started just before poor markets combined with high inflation, such as the late 1960s.

A few years later, three professors at Trinity University (Cooley, Hubbard and Walz) published what became known as the Trinity study. They examined success rates for different withdrawal rates, stock/bond mixes and time horizons. Their tables showed that a 4% inflation-adjusted withdrawal had a high historical success rate over 30 years for stock-heavy portfolios, and that success rates fell as withdrawal rates or time horizons rose.

Neither study promised that 4% is safe in the future. Both described what happened in the past under specific conditions.

The assumptions underneath

Before you lean on the rule, check whether its assumptions match your situation:

• A 30-year horizon. The original work was built for traditional retirees. Someone stopping work at 40 may need money for 50 years or more.
• U.S. market history. The 20th century was a strong period for U.S. markets. Other countries' histories were worse in some periods, and the future may differ from any past.
• A specific portfolio. The studies used broad stocks and bonds, usually with half or more in stocks. A very conservative or very concentrated portfolio behaves differently.
• No fees or taxes. The withdrawal is gross. Investment fees and taxes come out of it.
• Rigid spending. The method never cuts spending, even in a deep downturn. Real people usually do.
• “Success” means not hitting zero. Many successful paths ended with far more money than they started with; a few ended near empty. The rule says nothing about how stressful the ride was.

Where it breaks for early retirees

Longer horizons

Over longer periods, the margin for error shrinks because there are more years in which a bad sequence can hurt you. That's why many early retirees plan around 3.25% to 3.75% instead of 4%, or keep 4% but commit to spending flexibility. In multiplier terms, a 3.5% rate means about 28.6× spending and 3.25% means about 30.8×.

Starting conditions

The worst historical outcomes tended to follow periods when markets were expensive or when high inflation arrived early. You can't know in advance whether you're retiring into one of those, which is exactly why flexibility and cash buffers are worth planning for. See sequence-of-returns risk.

Taxes and account mix

If most of your money is in pre-tax accounts, part of every withdrawal goes to taxes. The 4% is what you take out, not what you get to spend. Our FIRE and taxes guide covers how to plan for that.

Health care and big lumpy costs

The rule assumes smooth, inflation-tracking spending. Real budgets have roofs, cars, and health premiums that can rise faster than inflation. Build those into your spending estimate before you multiply by 25.

What the rule gets right

For all its limits, the 4% rule is a good planning tool because:

• It turns a fuzzy goal (“enough”) into a concrete number.
• It reminds you that spending, not income, determines the target.
• It's based on long stretches of real history that include depressions, wars and high inflation, not just good years.

Use it to set a target and track progress. Then refine it.

Ways to make a withdrawal plan sturdier

Spending flexibility

Agreeing in advance to trim discretionary spending after poor market years can noticeably improve the odds of a plan lasting. A simple version: skip the inflation increase in any year after the portfolio fell.

Guardrails

Guardrail methods set an upper and lower band around your current withdrawal rate. If the rate drifts too high because the portfolio fell, you cut spending a set percentage; if it drifts low because the portfolio grew, you give yourself a raise.

Other income

Part-time work, a rental, or eventually Social Security reduces how much the portfolio must carry. Even a few years of modest earnings early in retirement reduces sequence risk. See Coast FIRE vs Barista FIRE.

A cash or bond buffer

Holding a year or two of spending in cash or short-term bonds can let you avoid selling stocks in a downturn. Our cash cushion and bucket strategy guide explains the trade-offs.

A worked illustration

Illustration only. Suppose a household plans to spend $60,000 a year.

The difference between 4% and 3.25% is about $346,000 in this illustration. Depending on savings rate, that may be several extra working years, which is why many people choose a middle path: aim for 25× to 28× and commit to flexibility rather than grinding out years for a very low withdrawal rate.

What to do this week

1. Write down your realistic annual retirement spending, including health insurance and lumpy costs.
2. Multiply it by 25, 26.7 and 28.6 to see your target at 4%, 3.75% and 3.5%.
3. Write a one-paragraph “bad year plan”: what spending you'd trim if markets fell 25% in your first year.

FIRE Danger Level: 3 of 5 when used blindly for a 50-year retirement; 1 of 5 when paired with flexibility.

The bottom line

The 4% rule is a historical observation, not a law of nature. It's a sensible anchor for a FIRE number, especially with a little extra margin and a willingness to adjust. Pair it with a realistic spending estimate, a plan for taxes and health care, and a strategy for bad early years, and it becomes a useful tool rather than a false promise. Try different rates in the FIRE number calculator.

This article is general education and not advice. The cast (Captain Compound, Frugal Fran, Lavish Larry, Doctor Drawdown) is fictional, and so are the example households. Your numbers will differ.