The 4% Rule: How Much Money You Actually Need to Stop Working

There is a question few people dare to formulate precisely: how much money do I actually need to never have to work again? Not roughly, not “a lot.” With a number.

The 4% rule is the most serious attempt that exists to answer that question. It is not perfect, it has conditions and limitations, but it is the most solid starting point we have.

Where the rule comes from

In 1998, three professors at Trinity University — Philip Cooley, Carl Hubbard, and Daniel Walz — published what would become known as the Trinity Study. They analysed historical US market data between 1926 and 1995 and asked: if someone retires with an investment portfolio and withdraws money each year, what percentage can they withdraw without the portfolio running out before 30 years?

The answer was 4%. With a portfolio composed of roughly 60% stocks and 40% bonds, withdrawing 4% in the first year and adjusting that amount for inflation in subsequent years produced a success rate above 95% across the historical periods studied.

The rule does not say that 4% is safe in every conceivable scenario. It says that historically, it has worked the vast majority of the time.

How the calculation works

The rule has a direct mathematical implication known as the 25× number: to find out how much capital you need, multiply your annual expenses by 25.

If you spend €24,000 per year, you need €600,000. If you spend €36,000 per year, you need €900,000. If you spend €48,000 per year, you need €1,200,000.

The reasoning: 4% of X = your annual expenses → X = annual expenses / 0.04 → X = annual expenses × 25.

That number — sometimes called the financial independence number — is the target. Not the point at which you stop working because you want to; the point at which working becomes a choice.

What the rule assumes (and what it does not)

The Trinity Study has conditions worth knowing before applying the rule.

It assumes a 30-year horizon. The study was designed with traditional retirement in mind — someone retiring at 65 and needing the money to last until 95. If you plan to retire at 40 and live to 90, your horizon is 50 years, not 30.

It assumes historical US market returns. The S&P 500 has historically posted high returns. An investor with a more global or more conservative portfolio might see different results.

It assumes you reinvest during good years. The sequence in which returns occur matters enormously. Retiring just before a market crash is far more dangerous than retiring just after one. This is known as sequence of returns risk.

It does not assume a state pension. If you will receive a public pension, that amount reduces what you need to withdraw from your portfolio, making the 4% rule even more conservative than necessary.

When 4% is not enough

For long retirements — more than 35 or 40 years — some researchers recommend using 3.5% or even 3%. The reason is simple: the longer the time horizon, the more variables come into play and the greater the probability that markets will go through prolonged periods of low returns.

Portfolio composition also matters. A pure fixed-income portfolio has historically lower returns and less capacity to absorb inflation over the long term. The 4% rule works best with significant equity exposure.

Finally, variable spending. The rule assumes your expenses are constant year after year. In practice, the early years of an early retirement tend to be more expensive — travel, projects, children at home — and so do the later years — healthcare, dependency care. That U-shaped spending profile may require somewhat more capital than the basic rule calculates.

How to apply it to your situation

The practical exercise has two steps.

First, calculate your actual annual expenses. Not the ones you think you have — the real ones. Add up twelve months of bank statements. Include irregular expenses: holidays, repairs, annual insurance, subscriptions. The result is your base number.

Second, decide which version of the rule to use. If you are 60 and planning a 30-year retirement, the original 4% is reasonable. If you are 40 and aiming for a 50-year retirement, 3.5% or 3% is more prudent. Divide your annual expenses by that percentage to get your target number.

No number guarantees anything. The future does not look exactly like the past. But without a concrete number, financial independence remains a vague wish. With a number, it becomes something you can move towards, month by month, with clarity.