Financial independence

The 4% rule: where it comes from, and when it breaks

It is the most quoted number in personal finance and the least examined. It came from a specific study, of a specific country, over a specific length of retirement — and if any of those do not describe you, the number changes.

Nirmal Amin 20 August 2026

Where it came from

In 1994 a financial adviser called William Bengen tested how much someone could withdraw from a portfolio without running out over a 30-year retirement, using historical US market returns. The answer was about 4% of the starting balance, adjusted upward each year for inflation. Later work at Trinity University tested variations and broadly agreed.

That is genuinely useful research. It is also research about 30 years, in the United States, with a portfolio of US stocks and bonds, over a period that includes some of the best equity returns in recorded history.

What it assumes, stated plainly

A 30-year horizon. Retire at 65, plan to 95. If you stop at 45, you are asking the number to do something it was never tested for.
Flat real spending. The same amount, inflation-adjusted, every year until you die. Real retirement spending tends to be higher early, lower in the middle, and higher again at the end.
US market history. Applied to other countries' historical returns, the safe rate is often lower.
No fees and no tax. A 1% platform and fund charge comes straight off the withdrawal rate.
No other income. No pension, no Social Security, no part-time work.

Why early retirees use less

A 50-year retirement is not a 30-year retirement with more of the same. The risk that a bad decade arrives early — sequence-of-returns risk — compounds with the length of the horizon, and it is the thing that actually kills plans. The average return can be exactly as assumed and the plan can still fail if the bad years land first.

The common adjustment is 3.5%, or 3.25% for a very long horizon. That sounds like a rounding difference and is not: at 40,000 of annual spending, 4% needs a million and 3.5% needs about 1.14 million. Half a percentage point of caution costs roughly three extra years of work.

Where the rule is too conservative

In fairness, the other direction exists too. Bengen's number is a worst-case survival rate — in most historical periods a 4% withdrawal left the retiree with more money than they started with. It also assumes you would keep spending the same amount while watching your portfolio halve, which almost nobody does.

Anyone who can cut spending in a bad year, or pick up some work, is materially safer than the model suggests. Flexibility is worth more than a lower withdrawal rate, and it is free.

What to do with it

Treat 4% as a headline estimate rather than a plan. Then check it against a projection that models your actual horizon and your actual other income — a pension arriving at 67 changes the answer more than the difference between 3.5% and 4%.

Our FIRE calculator shows both: the 25× rule figure, and the number your own ledger actually requires.

Common questions

Is the 4% rule still valid?

As a rough starting estimate, yes. As a plan for a retirement longer than thirty years, most practitioners now use 3.5% or lower. The rule was never a guarantee — it was the worst historical case in a specific data set, which is a useful thing to know and a different thing from a promise.

What is sequence of returns risk?

The risk that poor returns arrive early in retirement, while your portfolio is at its largest and you are selling into a falling market. Two retirements with identical average returns can end very differently depending only on the order those returns came in, which is why a flat-rate projection understates the danger.

Does the 4% rule work outside the United States?

Less well. It was derived from US market history, which was unusually strong over the tested period. Studies applying the same method to other developed markets generally produce lower safe withdrawal rates, which is an argument for caution rather than for a different rule.

Where this comes from

A withdrawal rate is a guess about spending

Whichever rate you choose, it is applied to your annual spending — so the accuracy of the whole exercise rests on that one figure. Tracking it properly is less exciting than debating 3.5 against 4, and it moves the answer more.

Not out yet. TLDR Money International is in build for the United States and the United Kingdom first, on iPhone and Android. The calculators are free and need no account.

Published 20 August 2026.