The financial independence movement (popularized under the acronym FIRE, Financial Independence, Retire Early) is built on an idea that's simple to state but demanding to execute: accumulate enough wealth that its returns cover your expenses indefinitely, without relying on a salary. The 4% rule is the most commonly used tool for estimating how much wealth that requires.
What financial independence is
Someone is considered to have reached financial independence when their invested wealth sustainably generates enough income to cover their living expenses, without needing to rely on a salary from work. It doesn't necessarily mean quitting work (some keep working by choice), but rather having the option of not depending on that income.
How the 4% rule works
The 4% rule states that if you withdraw 4% of your investment portfolio's value each year (adjusting that amount for inflation in subsequent years), you have a reasonably high probability that your wealth will last at least 30 years without running out, based on historical studies of returns from combined equity and fixed-income markets.
The inverse formula is the one typically used to set the target amount of wealth needed:
Wealth needed ≈ Desired annual spending × 25
If your annual expenses are €24,000, the target wealth under this rule would be roughly €600,000 (24,000 × 25).
Why the number 25 (or the 4%)
Multiplying by 25 is mathematically equivalent to dividing by 4%: they're the same relationship expressed in two different ways. That figure originates from historical studies of diversified portfolios (combining equities and fixed income) and their behavior over 30-year periods in the US market, with the corresponding limitations of applying that historical data to other markets or to future periods.
The main limitations of this rule
- It's based on historical data from specific markets (mainly the US), which doesn't guarantee identical behavior in the future or in other markets.
- It assumes a horizon of roughly 30 years; for someone seeking financial independence at a very young age, with a retirement horizon of 50 years or more, many experts recommend more conservative withdrawal rates, such as 3% or 3.5%.
- It doesn't account for one-off extraordinary expenses or significant lifestyle changes over the decades.
A guiding target, not a mathematical guarantee
The 4% rule is useful as a rough reference for setting a wealth target, but it shouldn't be read as an infallible mathematical guarantee. Periodically reviewing your actual situation, adjusting your withdrawal rate based on how markets actually perform, and keeping some flexibility in your spending are necessary complements to this simplified rule.
Calculate how much you'd need to accumulate
Our compound interest calculator lets you model how much time and what monthly contribution you'd need to reach the target wealth calculated with the 4% rule, under different return assumptions.