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This FIRE calculator estimates the capital you need to live off your investments (25 times your annual spending, the 4% rule) and how many years it takes to reach it with your current capital, your monthly savings and an expected return.
Capital needed to be free
600.000 €
Based on annual spending of 24.000 €
Current progress
8.3%You are 8.3% of the way to financial independence.
The 4% rule: It says you can withdraw 4% of your portfolio in the first year (adjusted for inflation thereafter) with a high probability that your money never runs out.
To work out your "FIRE number", multiply your target annual spending by 25.
Every year you start investing earlier, compounding sharply reduces the capital you have to put in yourself.
Using 7% is a sound baseline, since it strips an average 2-3% inflation out of the market's historical 10% return.
If you want to be more conservative, you can apply the 3% rule (spending x33), which increases your safety margin but requires more capital.
FIRE stands for Financial Independence, Retire Early. It is not necessarily about stopping work at 30, but about reaching the point where working becomes optional.
The philosophy rests on two pillars: aggressively raising your savings rate (living below your means) and investing that capital in diversified, low-cost index funds.
"Like Warren, I had a considerable passion to get rich, not because I wanted Ferraris — I wanted the independence. I desperately wanted it."
— Charlie Munger
This rule, drawn from the well-known "Trinity Study" at Trinity University, suggests that if you have accumulated 25 times your annual expenses, you can withdraw 4% of your portfolio in the first year (adjusting that amount for inflation thereafter) with a 95% probability of not running out of money over 30 years.
Our calculator uses this rule as the basis for your "FIRE number". That said, many investors prefer to be more conservative and target a 3% or 3.5% withdrawal rate for longer retirements (50+ years).
Your FIRE number is the invested capital that lets you withdraw what you spend each year without running out. The 4% rule sets it at 25 times your annual spending: with €2,000 a month (€24,000 a year) you need €600,000.
FIRE number = monthly spending × 12 × 25
For the timeline, the calculator starts from your current capital, adds your monthly savings and compounds it at the expected return divided by twelve until it reaches the target. It is the compound interest calculation in reverse: instead of asking how much you will have, it asks when you get there.
Four cases worked out with the calculator’s own function, at an annual return of 7 %. Change any input above to see your own case.
| Spending | FIRE number | Starting point | Time |
|---|---|---|---|
| €1,500 a month | €450,000 | €0 + €500/month | 26.3 years |
| €2,000 a month | €600,000 | €50,000 + €500/month | 23.3 years |
| €2,000 a month | €600,000 | €50,000 + €1,000/month | 17.9 years |
| €3,000 a month | €900,000 | €100,000 + €1,500/month | 16.9 years |
Assumptions: constant return, no taxes, no inflation and no state pension. They are the calculator’s; below we explain what changes in Spain.
Taxes. Withdrawing 4% usually means selling at a gain, and the gain is taxed in the savings base of Spanish income tax: 19% up to €6,000, 21% up to €50,000, 23% up to €200,000, 27% up to €300,000 and 30% above that (current scale, 2025 tax manual of the AEAT). If you want €2,000 net a month, your real FIRE number is somewhat above €600,000.
State pension. The 4% rule assumes living off the portfolio forever. In Spain, the state pension kicks in from retirement age and reduces what your investments must cover. The calculator does not include it: if retirement is far away, treat it as a cushion, not as part of the plan.
Inflation. Enter today’s spending and a real return (after inflation): 7% a year is a common reference for a global index portfolio. The calculator does not deduct fees; those of a robo-advisor or an ETF plan are in our index funds guide.
There is no single path. These four names describe how much capital you aim for and whether you keep working on the way.
It is the invested capital you need to live off its returns. It is calculated by multiplying your annual spending by 25, which equals withdrawing 4% a year: with €24,000 of annual spending, €600,000.
As a guide, yes; as a guarantee, no. It comes from the Trinity study with US data, and in Spain you must deduct income tax on gains when you withdraw. Many use 3.5% (spending × 29) to be safer.
With the 4% rule, €600,000 invested (2,000 × 12 × 25). With a 3.5% withdrawal rate, about €686,000. And if you want €2,000 net after tax, somewhat more: the calculator gives you the gross figure.
A real one, after inflation. A global index portfolio has historically returned around 7% nominal, which after inflation is closer to 4-5%. Try several: the calculator compares scenarios, it does not predict.
No. It calculates the capital to live off your investments alone. If you will retire with a pension, the capital you need from that age is lower; until then, your portfolio has to cover everything.
No. It is an educational tool that applies a general rule to the figures you enter, without knowing your tax or personal situation. To decide about your retirement, consult an adviser registered with the CNMV.